The chronicles of Bumblebee: The Hook, the Bee, and the Trickbot
connection
By Eli Salem
Published: 2022-04-27 · Archived: 2026-04-29 07:05:45 UTC
17 min read
Apr 27, 2022
In late March 2022, a new malware dubbed “Bumblebee” was discovered, and reported to be distributed in
phishing campaigns containing ISO files which eventually drop DLL files that contained the Bumblebee malware
itself.[1][3].
This malware deployment technique is not new, and several other malware has already been observed using it,
https://elis531989.medium.com/the-chronicles-of-bumblebee-the-hook-the-bee-and-the-trickbot-connection-686379311056
Page 1 of 45

most notably: BazarLoader, and IcedID[3]. Also, similar to the aforementioned malware, Bumblebee too was
observed delivering the Cobalt-Strike framework.
From a threat research perspective, what makes this malware interesting is the fact that it was associated with the
Conti ransomware group as one of the group's threat loaders[1].
In the past, the traditional loaders of Conti were Trickbot, Bazarloader, and Emotet, so it was quite intriguing to
inspect this malware closely.
In this article, I will present a code analysis of the Bumblebee malware, obviously, due to the malware's large size
I will not cover everything, and will focus on the parts that I think are the most interesting in terms of capabilities.
Also, one of my favorite topics in malware research is the ways of malware to avoid detection, so I will put more
emphasis on this subject as well.
Lastly, I divided the entire article into three parts, the table of contents is the following:
1. PART 1: The hook- unpacking the bumblebee’s crypter
- Unpacking mechanism
- Enters the hook
- Executing the code
- Bumblebee dropper high-level summary
2. PART 2: The bee- Investing the bumblebee’s payload
- Stolen anti-analysis code
- Searching for processes
- Searching registry keys
- Searching file paths
- Executing processes
- The little ones inside the flask: hiding additional DLLs
3. PART 3: The Trickbot connection- Investigating the hooking DLL
- Check for existing hooks
- Setting the hooks
- First hooks: Disable exceptions
- Second hooks: Further code execution
- The Trickbot hooking engine
- Static differences and code evolution
- Additional similarities
- Customize flattened RC4
- RapportGP.dll high-level summary
PART 1
The Hook: Unpacking the bumblebee’s crypter
Hash: a9c8b7c411571700e6ea03e4e48ddb896a33e53e
https://elis531989.medium.com/the-chronicles-of-bumblebee-the-hook-the-bee-and-the-trickbot-connection-686379311056
Page 2 of 45

Press enter or click to view image in full size
Bumblebee dropper as seen in PEstudio
The initial dropper of Bumblebee is a 64bit file, with relatively high entropy which indicates a possibly obfuscated
\ encrypted content that will be decrypted in runtime.
The DLL itself contains two export functions: InternalJob and SetPath. Also, the file’s internal name appears to be
“lodqcbw041xd9.dll”.
Bumblebee dropper exports and internal name in PE-Bear
Unpacking mechanism
https://elis531989.medium.com/the-chronicles-of-bumblebee-the-hook-the-bee-and-the-trickbot-connection-686379311056
Page 3 of 45

Once we enter the loader’s main function, we see that it is unique, and does not look like any common crypters
that can be found in Conti’s loaders (such as Emotet or Bazarloader).
Bumblebee loader\crypter main
As we open the loader in IDA, we see that the majority of the PE in the IDA navigator has the olive color which
means unexplored bytes. This is common when there is some content in the PE that needs to be decrypted during
runtime.
Press enter or click to view image in full size
Bumblebee loader unexplored bytes
Tip: During my analysis, I disabled the file’s ASLR to match the addresses in IDA and Xdbg, this is super helpful
and saves a lot of time.
To do so, open the file in CFF explorer, and then:
1. Click Optional Header
2. Go to DllCharacteristics
3. Remove the V from “DLL can move”
Press enter or click to view image in full size
https://elis531989.medium.com/the-chronicles-of-bumblebee-the-hook-the-bee-and-the-trickbot-connection-686379311056
Page 4 of 45

Disabling ASLR
Next, we can see that the DllEntryPoint is an empty export function, so we will want to redirect our execution
flow to one of the working export functions, for this case, we will choose “SetPath”.
To redirect the flow, do the following:
1. In IDA \ PE-Bear, copy the address of the required export function
2. In Xdbg, right click on RIP
3. Click on “Modify Value”
4. Paste the address of the export function
Press enter or click to view image in full size
https://elis531989.medium.com/the-chronicles-of-bumblebee-the-hook-the-bee-and-the-trickbot-connection-686379311056
Page 5 of 45

Changing the address
After clicking OK we will find ourselves at the beginning of the export function. This trick can be used in any
other malware the executed via designated export function
Bumblebee SetPath
From a reverse engineer perspective, the crypter is an inconvenient binary to inspect, and there are not many
“quick wins” we can gather just by looking at it, however, this crypter is unique in today's landscape so I will
focus on the areas I found are the most interesting.
First, the crypter will start with a traditional unpacking activity, in the function sub_180003490 there are two other
functions:
1. sub_1800021D0 - which will allocate virtual memory using HeapAlloc (this function will happen multiple
times during the crypter unpacking)
2. sub_1800029BC - Which gets an embedded content and writes it into the newly allocated memory
Press enter or click to view image in full size
https://elis531989.medium.com/the-chronicles-of-bumblebee-the-hook-the-bee-and-the-trickbot-connection-686379311056
Page 6 of 45

Bumblebee loader\crypter main
Then, the function sub_180002FF4 will be executed to do the following:
1. Allocate new virtual memory using the same sub_1800021D0 function.
2. Manipulate the content from the first allocated buffer and write the output into the newly allocated memory
Press enter or click to view image in full size
Bumblebee loader\crypter main
The next step will be the function sub_180004180, this function will do the following:
1. It executes a function named sub_180001670 that will allocate multiple virtual memories using the already
mentioned sub_1800021D0.
2. Call the function named sub_180003CE that will use the virtual memory that was allocated in
sub_180002FF4, do additional manipulations, and eventually writes an unpacked MZ into the last
allocated buffer from the function sub_180001670.
Press enter or click to view image in full size
https://elis531989.medium.com/the-chronicles-of-bumblebee-the-hook-the-bee-and-the-trickbot-connection-686379311056
Page 7 of 45

Bumblebee loader\crypter main
When looking statically in the function sub_180003CE, the loop that will write the unpacked file will be the
following:
Bumblebee loader payload decryption
And when observing dynamically, it will look like the following:
Press enter or click to view image in full size
Bumblebee loader payload decryption
In the end, we get an allocated memory with Read-Write permissions with an unpacked payload inside.
https://elis531989.medium.com/the-chronicles-of-bumblebee-the-hook-the-bee-and-the-trickbot-connection-686379311056
Page 8 of 45

Bumblebee loader payload decrypted in process hacker
Until now, everything that is observed are things that are pretty much common in other loaders \ crypters,
however, we still have two unsolved questions:
1. The code section of the payload does not have Execute permission, so it cant run.
2. What makes this loader special?
Enters the hook
The loader will enter a function called sub_180001000, this function will create inline hooks[5] that will ignite the
chain of events that will lead to the code execution.
https://elis531989.medium.com/the-chronicles-of-bumblebee-the-hook-the-bee-and-the-trickbot-connection-686379311056
Page 9 of 45

Bumblebee loader payload decryption
As we enter, we notice something interesting, the loader assign functions to a memory address, then it will call
another function named sub_100025EC.
Assign functions to addresses
This function will do the following:
1. Get Ntdll handle with LoadLibrary
2. Get the address of NtOpenFile
3. Get the address of NtCreateSection
4. Get the address of NtMapViewOfSection
5. Return the data
https://elis531989.medium.com/the-chronicles-of-bumblebee-the-hook-the-bee-and-the-trickbot-connection-686379311056
Page 10 of 45

Getting NT functions
To observe it dynamically, we can just go to the debugger and step over the functions themselves.
Press enter or click to view image in full size
Getting NT functions
After exiting sub_100025EC, our attention will go to a function named sub_1800037C4. This function will be
responsible to install a hook in the aforementioned NT functions.
It will do it in the following way:
1. Call VirtualProtect to change the protection of the area it wants to write into to be writeable
2. Call sub_180002978 that will take as arguments:
1. The function to write into
2. The content it wants to write
3. The size
3. Call VirtualProtect to change the protection again to not be writeable
https://elis531989.medium.com/the-chronicles-of-bumblebee-the-hook-the-bee-and-the-trickbot-connection-686379311056
Page 11 of 45

Setting hook
Eventually, this activity will occur inside a loop to install the hooks in each of the NT functions. The hook that
will be installed will be the functions that have been assigned to memory addresses at the beginning of the larger
function.
1. sub_180001D4 for NtMapViewOfSection
2. sub_1800023D4 for NtOpenFile
3. sub_1800041EC for NtCreateSection
If we wanted to observe the changes dynamically we have two options, the first one is to just observe it in the
debugger by step over sub_180002978
Hooked NT functions
Another option is to use the took Hollow hunter[6] with the “/hooks” as an argument. Then, we will have a .tag
file from the hooked DLL (if found of course)
https://elis531989.medium.com/the-chronicles-of-bumblebee-the-hook-the-bee-and-the-trickbot-connection-686379311056
Page 12 of 45

View hooks using hollow hunter
And when we open this file with a text editor we could see the indication of who are the hooked function, and
where the hook itself lies.
Press enter or click to view image in full size
View hooks using hollow hunter
To summarize the hooking procedure, it will look like this:
Press enter or click to view image in full size
https://elis531989.medium.com/the-chronicles-of-bumblebee-the-hook-the-bee-and-the-trickbot-connection-686379311056
Page 13 of 45

Bumblebee loader install hook mechanism
Executing the code
After we finish setting the hooks, we will head to the function sub_1800013A0
Bumblebee loader\crypter main
This function will attempt to execute the DLL “GdiPlus.dll” using the API call LoadLibrary, with SetPath as an
export function.
https://elis531989.medium.com/the-chronicles-of-bumblebee-the-hook-the-bee-and-the-trickbot-connection-686379311056
Page 14 of 45

LoadLibrary loading GdiPlus.dll
LoadLibrary loading GdiPlus.dll
Q: Why does the malware even want to use GdiPlus.dll?
A: It doesn't.
Q: So why the need to load it?
A: Because it is not loaded (wait what?!)
The malware will attempt to use some (and unique) custom unpacking:
1. When LoadLibrary loads a DLL file, it uses internally the hooked NT function as part of its internal
activity.
2. The malware chooses a DLL that is not loaded yet.
3. NtOpenFile will get a file handle of GdiPlus.dll
4. NtCreateSection will create a section for the file handle of GdiPlus.dll
However, here is when things become tricky, when the LoadLibrary will try to use MapViewOfSection to map the
GdiPlus.dll section, the hook function of MapViewOfSection (sub_180001D4C) will do the following:
1. It will use CreateSection to create a new section with READ-WRITE-EXECUTE permissions, without any
file handle to associate it with.
2. It will write the unpacked malicious content into this section
3. It returns NTSTATUS_SUCCESS to the LoadLibrary so it will seem to it as if GdiPlus.dll was mapped
successfully.
Press enter or click to view image in full size
https://elis531989.medium.com/the-chronicles-of-bumblebee-the-hook-the-bee-and-the-trickbot-connection-686379311056
Page 15 of 45

Hooked NtMapViewOfSection mechanism
The result will be an unpacked bumblebee malware that resides in the RWX section and is associated with
GdiPlus.dll. Interestingly, the GdiPlus.dll is considered a relocated DLL in Process hacker.
Press enter or click to view image in full size
Relocated module point to RWX section
Bumblebee dropper high lever summary
If we want to look at all the dropper unpacking mechanism steps in a high-level overview and summarize them
into three steps, it will look like this:
Press enter or click to view image in full size
https://elis531989.medium.com/the-chronicles-of-bumblebee-the-hook-the-bee-and-the-trickbot-connection-686379311056
Page 16 of 45

Bumblebee dropper overview
PART 2
The bee: Investigating the bumblebee’s payload
Press enter or click to view image in full size
https://elis531989.medium.com/the-chronicles-of-bumblebee-the-hook-the-bee-and-the-trickbot-connection-686379311056
Page 17 of 45

Unpacked Bumblebee payload
The unpacked malware is a large 64-bit file with quite high entropy.
This file appears to be the core component of the Bumblebee malware. It features many traditional capabilities we
would expect from malware, such as internet communication, file manipulation, collecting user information,
cryptography libraries, etc.
In my article I will not cover this file as much because of scoping decisions, however, some interesting code parts
to mention are:
Stolen anti-analysis code
As with many malware, Bumblebee also has anti-analysis tricks, however, the majority of them are grouped in one
large function. Also, During my observation, I notice that additional anti-analysis checks have been added as time
goes by, which indicates a quick evolving malware or that the authors are still in the “testing the waters” phase.
In addition, this entire anti-analysis function code is taken from the GitHub page of the “al-khaser project”[7]. For
good measure, I will show some examples.
Searching for processes
The malware will search for multiple tools that are being used for dynamic and static malware analysis tools. The
malware will iterate through the processes using CreateToolHelp32Snapshot.
Press enter or click to view image in full size
https://elis531989.medium.com/the-chronicles-of-bumblebee-the-hook-the-bee-and-the-trickbot-connection-686379311056
Page 18 of 45

Searching for processes in Bumblebee
As said, this code is the exact code found in the al-khaser project.
https://elis531989.medium.com/the-chronicles-of-bumblebee-the-hook-the-bee-and-the-trickbot-connection-686379311056
Page 19 of 45

al-khaser source code
The malware also attempts to detect any kind of virtualization environment with the detection of their processes, it
varies from Vmware to Vbox processes.
Searching for Vmware processes in Bumblebee
Searching registry keys
The malware will attempt to search for designated registry keys that indicate any kind of virtual environment from
multiple products.
https://elis531989.medium.com/the-chronicles-of-bumblebee-the-hook-the-bee-and-the-trickbot-connection-686379311056
Page 20 of 45

Searching for Vmware registry key in Bumblebee
Searching file paths
Get Eli Salem’s stories in your inbox
Join Medium for free to get updates from this writer.
Remember me for faster sign in
The malware will search for file paths that can indicate any kind of virtual environment.
Searching for VBOX files in Bumblebee
At this point, it will be useless to continue writing the anti-analysis capabilities, so for those who want to see all,
please visit the al-khaser project GitHub page.
Executing processes
https://elis531989.medium.com/the-chronicles-of-bumblebee-the-hook-the-bee-and-the-trickbot-connection-686379311056
Page 21 of 45

Among the malware, capabilities are to execute Rundll.exe to run the DLL with the InternalJob as an export
function using Wscript.
Executing Wscript
Also, the malware can use PowerShell to perform further activities
Executing PowerShell
The little ones inside the flask
One of the most interesting things about the Bumblebee core component is the fact that it contains two DLL files
inside of him.
Press enter or click to view image in full size
https://elis531989.medium.com/the-chronicles-of-bumblebee-the-hook-the-bee-and-the-trickbot-connection-686379311056
Page 22 of 45

Two hidden DLL files inside the unpacked Bumblebee
Both of these files have the same internal name RapportGP.dll (which is also used by the security company
Trusteer)
Bumblebee hooking DLL aka RapportGP.dll
The two DLL files are completely identical except for the fact that one of them is 32-bit and the other is 64-bit.
PART 3: The shadow of Trickbot- Investigating the hooking DLL
In the last part, I will investigate the RapportGP.dll, as said, there are two versions: 32\64 bit, and for my analysis,
I will focus only on the 32 bit.
The main concept behind RapportGP.dll is hooking, and the entire module’s mechanism is supporting this activity.
Check for existing hooks
One of the first activities of the module occurs in a function named “sub_100060C0”, in general, this function will
be responsible to check if there is any hooked function from a list of pre-determined functions.
Inside sub_100060C0, the chain of events that leads to this is the following:
https://elis531989.medium.com/the-chronicles-of-bumblebee-the-hook-the-bee-and-the-trickbot-connection-686379311056
Page 23 of 45

1. A handle to Ntdll.dll, Kernel32.dll, Kernelbase.dll, Advapi32.dll obtained
2. The requested DLL’s path obtained
3. A call to the function sub_100059B0 was made to get a copy of NtProtectVirtualMemory that stored in the
allocated memory
4. The arguments are sent to another function named sub_10005B90
Press enter or click to view image in full size
1. RapportGP.dll checking and disabling existing hooks
The functions it wants to check are:
In Ntdll.dll
https://elis531989.medium.com/the-chronicles-of-bumblebee-the-hook-the-bee-and-the-trickbot-connection-686379311056
Page 24 of 45

RapportGP.dll list of Ntdll functions to check
In Kernel32.dll
https://elis531989.medium.com/the-chronicles-of-bumblebee-the-hook-the-bee-and-the-trickbot-connection-686379311056
Page 25 of 45

RapportGP.dll list of Kernel32 functions to check
In Kernelbase.dll
RapportGP.dll list of Kernelbase functions to check
In Advapi32.dll
https://elis531989.medium.com/the-chronicles-of-bumblebee-the-hook-the-bee-and-the-trickbot-connection-686379311056
Page 26 of 45

RapportGP.dll list of Advapi32 functions to check
In sub_10005B90, the module path of the requested DLL file will be mapped to memory and will be sent to an
additional function named “sub_10005D40” that will deal with the actual checking.
Press enter or click to view image in full size
2. RapportGP.dll checking and disabling existing hooks
As for the checks themselves, it is quite simple:
1. The malware iterate through the export functions of the legitimate DLL file that was mapped to memory by
the process when it loads.
2. The malware will check if the name is one of the function names it wants to check
3. Once found, the malware calls sub_10001040 that checks for hooks evidence in the DLL that was mapped
by the process loader
4. The malware will do the same for the DLL that was mapped by the malware itself (in sub_10005B90).
5. If no hooks are found, it will continue to iterate
Press enter or click to view image in full size
https://elis531989.medium.com/the-chronicles-of-bumblebee-the-hook-the-bee-and-the-trickbot-connection-686379311056
Page 27 of 45

3. RapportGP.dll checking and disabling existing hooks
And if there is an indication of hooks, the malware does the following
1. Get information about the original function
2. It will change the protection
3. Check if it's writable
4. Write the content of the mapped function to the original function. In this way, it restores it to the state it
should be if there are no hooks.
Press enter or click to view image in full size
https://elis531989.medium.com/the-chronicles-of-bumblebee-the-hook-the-bee-and-the-trickbot-connection-686379311056
Page 28 of 45

4. RapportGP.dll checking and disabling existing hooks
If we wanted to observe this activity dynamically, all we need to do is to change the bytes from the beginning of
one of the functions the malware wants to check. For example, let's take NtCreateFile.
1. Original function at 775222C0
2. The function that mapped by the malware at 02E022C0
5. RapportGP.dll checking and disabling existing hooks
When looking in the dump, we can see that their code is exactly the same
https://elis531989.medium.com/the-chronicles-of-bumblebee-the-hook-the-bee-and-the-trickbot-connection-686379311056
Page 29 of 45

6. RapportGP.dll checking and disabling existing hooks
Let's change the first byte of the original to have an E9 opcode (jump)
Press enter or click to view image in full size
7. RapportGP.dll checking and disabling existing hooks
Now, if we will try to debug dynamically, we will be able to get to the last part of the code.
Press enter or click to view image in full size
8. RapportGP.dll checking and disabling existing hooks
After stepping over memset, we can see that the E9 byte no longer exists and the original function returned to its
normal state.
https://elis531989.medium.com/the-chronicles-of-bumblebee-the-hook-the-bee-and-the-trickbot-connection-686379311056
Page 30 of 45

9. RapportGP.dll checking and disabling existing hooks
At a very high level, the process eventually looks like this:
Press enter or click to view image in full size
10. RapportGP.dll checking and disabling existing hooks
Setting the hooks
After checking that there are no other hooks, the malware turns to set its own hooks. The malware will have two
kinds of hooks for different purposes.
First hooks: Disable Exceptions
The malware will set a hook on the function RaiseFailFastException which is located in kernel32.dll and api-ms-win-core-errorhandling-l1–1–2.dll.
The function that will be triggered will be empty, therefore no exception will be triggered.
https://elis531989.medium.com/the-chronicles-of-bumblebee-the-hook-the-bee-and-the-trickbot-connection-686379311056
Page 31 of 45

Press enter or click to view image in full size
RapportGP.dll hooks to disable exceptions
Second hooks: Further code execution
The malware will use the same technique the bumblebee loader did. It will first get the addresses of the function
ZwMapViewOfSection, ZwOpenSection, ZwCreateSection, ZwOpenFile, ZwClose, and LdrLoadDll.
RapportGP.dll second hooks
And similar to the Bumblebee’s loader, it will first set the hook, and then will call LdrLoadDll which is the lower
lever equivalent of LoadLibrary to load the module “wups.dll”, which will trigger the chain of events we already
discussed in the Bumblebee loader part.
https://elis531989.medium.com/the-chronicles-of-bumblebee-the-hook-the-bee-and-the-trickbot-connection-686379311056
Page 32 of 45

RapportGP.dll second hooks
The Trickbot hooking engine
Although both hooks are doing completely different things, the hooks’ installation mechanism is the same.
Interestingly, this mechanism is also the same as the web-inject module of Trickbot.
Press enter or click to view image in full size
https://elis531989.medium.com/the-chronicles-of-bumblebee-the-hook-the-bee-and-the-trickbot-connection-686379311056
Page 33 of 45

Bumblebee’s RapportGP.dll vs Trickbot’s web-inject module
As with many ex-bankers that use hooking such as Panda, Trickbot, and Qbot, their hooking code is based on the
Zeus leak, however, each of them has its flavor and changes and Trickbot is no different.
In the Trickbot web-inject hooking mechanism, which has already been documented[8], when creating the inline
hooking “trampoline” there is the following evasion technique:
1. Trickbot writes 35 bytes of NOPS (0x90)
2. Add the traditional function prologue
3. Write the jump to the targeted function at the end of the NOPS
https://elis531989.medium.com/the-chronicles-of-bumblebee-the-hook-the-bee-and-the-trickbot-connection-686379311056
Page 34 of 45

Trickbot’s web-inject module evasion technique
As we debug Bumblebee, we notice it uses the same unique evasion as well (adjusted for the API calls it wants to
hook). So for example when hooking the ZwMapViewOfSection, which instantiates a Syscall, it will look like this.
Bumblebee’s RapportGP.dll evasion technique
And when targeting the user-mode functions RaiseFailFastException, it will look exactly like in Trickbot.
https://elis531989.medium.com/the-chronicles-of-bumblebee-the-hook-the-bee-and-the-trickbot-connection-686379311056
Page 35 of 45

Bumblebee’s RapportGP.dll evasion technique
Static differences and code evolution
When inspecting the entire code flow graph of the hook installation function, we can see a striking similarity
between Bumblebee’s RapportGP.dll and Trickbot’s web-inject module.
Press enter or click to view image in full size
https://elis531989.medium.com/the-chronicles-of-bumblebee-the-hook-the-bee-and-the-trickbot-connection-686379311056
Page 36 of 45

Bumblebee’s RapportGP.dll vs Trickbot’s web-inject module install hook functions
Interestingly, although the actual functionality is the same, we might think that statically everything is the same,
even the sub-functions inside the hooking installation function. Funny enough, this is not the case.
As mentioned above, in the hooking installation function, one function is responsible for doing checks and return
size (Please see the image above).
1. In Trickbot its sub_10001650
2. In Bumblebee its sub_10002870
However, when inspecting their code and code flow statically, this is how they both look like
Press enter or click to view image in full size
https://elis531989.medium.com/the-chronicles-of-bumblebee-the-hook-the-bee-and-the-trickbot-connection-686379311056
Page 37 of 45

Bumblebee’s RapportGP.dll vs Trickbot’s web-inject module- same functionality, different flow
Obviously, in Bumblebee, the authors have decided to use Control-flow-flattening[9] to obfuscate the entire flow
of the function. For those of you who are not familiar with this obfuscation technique, I strongly recommend the
following video[10].
In addition, inside each of these functions (sub_10001650 in Trickbot, sub_10002870 in Bumblebee) there are 3
functions (one of them is memset), and the Control-flow-flattening concept continues in Bumblebee inside them as
well.
For example, here are another two functions that act the same dynamically:
Press enter or click to view image in full size
https://elis531989.medium.com/the-chronicles-of-bumblebee-the-hook-the-bee-and-the-trickbot-connection-686379311056
Page 38 of 45

Bumblebee’s RapportGP.dll vs Trickbot’s web-inject module- same functionality, different flow
When observing the two functions in Bindiff flow graphs, we could see some similarities.
https://elis531989.medium.com/the-chronicles-of-bumblebee-the-hook-the-bee-and-the-trickbot-connection-686379311056
Page 39 of 45

Bumblebee’s RapportGP.dll vs Trickbot’s web-inject module-Bindiff
Additional similarities
In both modules, there are other functions that are not completely identical by code, however, they serve the same
functionality.
Example_1
Before entering the hooking functions, both Trickbot and Bumblebee attempt to use LoadLibrary and get the
address of the function it wants to hook.
https://elis531989.medium.com/the-chronicles-of-bumblebee-the-hook-the-bee-and-the-trickbot-connection-686379311056
Page 40 of 45

The difference is that in Trickbot it explicitly writes “Kernel32.dll” and in Bumblebee it gets the DLL’s name from
the caller function.
Press enter or click to view image in full size
Bumblebee’s RapportGP.dll vs Trickbot’s web-inject module- same functionality, a different
approach
Example_2
The call for the hooking activity looks very similar as well
https://elis531989.medium.com/the-chronicles-of-bumblebee-the-hook-the-bee-and-the-trickbot-connection-686379311056
Page 41 of 45

Bumblebee’s RapportGP.dll vs Trickbot’s web-inject module
Example_3
Outside the hooking, the Bumblebee’s hooking module starts with getting the process handle and eventually
duplicating a thread handle, whereas, the Trickbot’s module starts with getting the process handle and duplicating
the token. Again, the same objective, in a different way.
Customize flattened RC4
Another interesting activity lies inside the hooked ZwMapViewOfSection function. The hook appears to use a
customize RC4 obfuscated with the Control-flow-flattening technique.
https://elis531989.medium.com/the-chronicles-of-bumblebee-the-hook-the-bee-and-the-trickbot-connection-686379311056
Page 42 of 45

Custom RC4 with CFF obfuscation
RapportGP.dll High-level summary
When trying to summarize the entire file behavior, it eventually is the following:
Press enter or click to view image in full size
https://elis531989.medium.com/the-chronicles-of-bumblebee-the-hook-the-bee-and-the-trickbot-connection-686379311056
Page 43 of 45

RapportGP.dll overall activity
Conclusion
https://elis531989.medium.com/the-chronicles-of-bumblebee-the-hook-the-bee-and-the-trickbot-connection-686379311056
Page 44 of 45

The bumblebee malware is a very interesting piece of code, and to perform their objectives, the authors show a
high level of creativity and innovation.
The interesting similarities between the Bumblebee hooking DLL and the Trickbot’s web-inject DLL raise
questions and speculations.
On one hand, the similarities are not strong enough to deduce that the authors of Bumblebee and Trickbot are the
same, on the other hand, it is not far-fetched to assume that the authors of Bumblebee have the source code of the
Trickbot’s web-inject module.
In any case, the authors took an already proven and working code and evolve it to be less detectable to AV
products, and challenging to security researchers.
References
[1] https://blog.google/threat-analysis-group/exposing-initial-access-broker-ties-conti/
[2] https://twitter.com/Unit42_Intel/status/1512146449345171459
[3] https://www.cynet.com/orion-threat-alert-flight-of-the-bumblebee/
[4] https://github.com/hasherezade/pe-bear-releases
[5] https://youtu.be/9efJ8_ukxlY?t=2
[6] https://github.com/hasherezade/hollows_hunter
[7] https://github.com/LordNoteworthy/al-khaser/tree/master/al-khaser
[8] https://www.sentinelone.com/labs/how-trickbot-malware-hooking-engine-targets-windows-10-browsers/
[9] https://blog.jscrambler.com/jscrambler-101-control-flow-flattening
[10] https://youtu.be/SulC2l1Dvbo
IOC
bumblebee_dropper: 4a35fa2f0903f7ba73ac21564a5a0e2a25374e10
bumblebee_malware: 5dbb3bbc57653c348be7778628ed0ef11ffef35d
bumblebee_rapportgp: 5c8f7465ba67138e58d3ca61e4346e31c2b799d8
Trickbot web-inject module: 0785D0C5600D9C096B75CC4465BE79D456F60594
Source: https://elis531989.medium.com/the-chronicles-of-bumblebee-the-hook-the-bee-and-the-trickbot-connection-686379311056
https://elis531989.medium.com/the-chronicles-of-bumblebee-the-hook-the-bee-and-the-trickbot-connection-686379311056
Page 45 of 45

 https://elis531989.medium.com/the-chronicles-of-bumblebee-the-hook-the-bee-and-the-trickbot-connection-686379311056  
Searching for processes in Bumblebee 
As said, this code is the exact code found in the al-khaser project.
   Page 19 of 45