{
	"id": "0198df17-ed24-487f-ba3e-e927650da1b3",
	"created_at": "2026-04-06T00:22:15.276548Z",
	"updated_at": "2026-04-10T13:12:53.04196Z",
	"deleted_at": null,
	"sha1_hash": "dc27771dfc5c0566d5ae9dd7fcf617189ede19d6",
	"title": "Worm.Win32.PYFILEDEL.AA - Threat Encyclopedia | Trend Micro (US)",
	"llm_title": "",
	"authors": "",
	"file_creation_date": "0001-01-01T00:00:00Z",
	"file_modification_date": "0001-01-01T00:00:00Z",
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	"plain_text": "Worm.Win32.PYFILEDEL.AA - Threat Encyclopedia | Trend\r\nMicro (US)\r\nBy Analysis by: Carl Maverick Pascual\r\nArchived: 2026-04-05 14:20:24 UTC\r\nThis Worm arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users\r\nwhen visiting malicious sites.\r\nIt drops copies of itself in removable drives. These dropped copies use the names of the folders located on the said\r\ndrives for their file names.\r\nArrival Details\r\nThis Worm arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users\r\nwhen visiting malicious sites.\r\nInstallation\r\nThis Worm drops a copy of itself in the following folders using different file names:\r\n%System Root%\\boots\\syswin.exe\r\n(Note: %System Root% is the Windows root folder, where it usually is C:\\ on all Windows operating system\r\nversions.)\r\nIt adds the following processes:\r\ntasklist.exe /fo csv\r\n%System Root%\\boots\\syswin.exe\r\n(Note: %System Root% is the Windows root folder, where it usually is C:\\ on all Windows operating system\r\nversions.)\r\nIt creates the following folders:\r\n%System Root%\\boots\r\n(Note: %System Root% is the Windows root folder, where it usually is C:\\ on all Windows operating system\r\nversions.)\r\nAutostart Technique\r\nThis Worm adds the following registry entries to enable its automatic execution at every system startup:\r\nhttps://www.trendmicro.com/vinfo/us/threat-encyclopedia/malware/worm.win32.pyfiledel.aa\r\nPage 1 of 5\n\nHKEY_CURRENT_USER\\Software\\Microsoft\\\r\nWindows\\CurrentVersion\\Run\r\nsyswin = \"%System Root%\\boots\\syswin.exe\"\r\nPropagation\r\nThis Worm searches for folders in all physical and removable drives then drops copies of itself inside the folder as\r\n{folder name}.EXE.\r\nIt drops copies of itself in removable drives. These dropped copies use the names of the folders located on the said\r\ndrives for their file names.\r\nOther Details\r\nThis Worm does the following:\r\nIt modifies .exe files in all drives and directory to a size of zero byte, making it unusable.\r\nStep 1\r\nBefore doing any scans, Windows XP, Windows Vista, and Windows 7 users must disable System Restore to allow\r\nfull scanning of their computers.\r\nStep 2\r\nNote that not all files, folders, and registry keys and entries are installed on your computer during this\r\nmalware's/spyware's/grayware's execution. This may be due to incomplete installation or other operating system\r\nconditions. If you do not find the same files/folders/registry information, please proceed to the next step.\r\nStep 3\r\nRestart in Safe Mode\r\n[ Learn More ]\r\nStep 4\r\nDelete this registry value\r\n[ Learn More ]\r\nImportant: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this\r\nstep only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft\r\narticle first before modifying your computer's registry.\r\n \r\nIn HKEY_CURRENT_USER\\Software\\Microsoft\\Windows\\CurrentVersion\\Run\r\nsyswin = \"%System Root%\\boots\\syswin.exe\"\r\nhttps://www.trendmicro.com/vinfo/us/threat-encyclopedia/malware/worm.win32.pyfiledel.aa\r\nPage 2 of 5\n\nStep 5\r\nSearch and delete these folders\r\n[ Learn More ]\r\nPlease make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option\r\nto include all hidden folders in the search result.\r\n%System Root%\\boots\r\nStep 6\r\nRestart in normal mode and scan your computer with your Trend Micro product for files detected as\r\nWorm.Win32.PYFILEDEL.AA. If the detected files have already been cleaned, deleted, or quarantined by your\r\nTrend Micro product, no further step is required. You may opt to simply delete the quarantined files. Please check\r\nthis Knowledge Base page for more information.\r\nStep 7\r\nRestore a file/s that has/have been corrupted/modified by this malware/grayware\r\nTo restore system files:\r\n• For Windows 2000:\r\n1. Insert your Windows 2000 Installation CD in your CD-ROM drive.\r\n2. Click Start\u003eRun.\r\n3. In the Open text box, type the following then click OK:\r\nexpand D:\\i386\\{file to restore}.ex_ %windir%\\system32\\{file to restore}.exe\r\n(Note: In the example above, D: refers to the CD-ROM drive. If your CD-ROM drive is not D:, please\r\nchange the letter accordingly. Also, the file to restore is C:\\WINNT\\System32\\explorer.exe.)\r\n• For Windows XP and Windows Server 2003:\r\n1. Click Start\u003eRun.\r\n2. In the Open text box, type the following then click OK:\r\nMSCONFIG\r\nhttps://www.trendmicro.com/vinfo/us/threat-encyclopedia/malware/worm.win32.pyfiledel.aa\r\nPage 3 of 5\n\n3. Make sure that the option Normal startup - load all device drivers and services option is selected.\r\n4. Click the Expand button.\r\n5. In the dialog box that appears, type the following:\r\nWherein:\r\nFile to restore contains the path and file name of the file you wish to restore.\r\nRestore from contains the path to the Windows CAB files. This path may vary from machine to\r\nmachine. It may be in a local drive, in a network drive, or in a CD-ROM. In the local drive, it is\r\nhttps://www.trendmicro.com/vinfo/us/threat-encyclopedia/malware/worm.win32.pyfiledel.aa\r\nPage 4 of 5\n\nusually in C:\\WINDOWS\\OPTIONS\\INSTALL.\r\nSave file in contains the path of the file you wish to restore (Do not include the file name).\r\n6. Click the Expand button.\r\nDid this description help? Tell us how we did.\r\nSource: https://www.trendmicro.com/vinfo/us/threat-encyclopedia/malware/worm.win32.pyfiledel.aa\r\nhttps://www.trendmicro.com/vinfo/us/threat-encyclopedia/malware/worm.win32.pyfiledel.aa\r\nPage 5 of 5",
	"extraction_quality": 1,
	"language": "EN",
	"sources": [
		"Malpedia"
	],
	"origins": [
		"web"
	],
	"references": [
		"https://www.trendmicro.com/vinfo/us/threat-encyclopedia/malware/worm.win32.pyfiledel.aa"
	],
	"report_names": [
		"worm.win32.pyfiledel.aa"
	],
	"threat_actors": [
		{
			"id": "d90307b6-14a9-4d0b-9156-89e453d6eb13",
			"created_at": "2022-10-25T16:07:23.773944Z",
			"updated_at": "2026-04-10T02:00:04.746188Z",
			"deleted_at": null,
			"main_name": "Lead",
			"aliases": [
				"Casper",
				"TG-3279"
			],
			"source_name": "ETDA:Lead",
			"tools": [
				"Agentemis",
				"BleDoor",
				"Cobalt Strike",
				"CobaltStrike",
				"RbDoor",
				"RibDoor",
				"Winnti",
				"cobeacon"
			],
			"source_id": "ETDA",
			"reports": null
		},
		{
			"id": "aa73cd6a-868c-4ae4-a5b2-7cb2c5ad1e9d",
			"created_at": "2022-10-25T16:07:24.139848Z",
			"updated_at": "2026-04-10T02:00:04.878798Z",
			"deleted_at": null,
			"main_name": "Safe",
			"aliases": [],
			"source_name": "ETDA:Safe",
			"tools": [
				"DebugView",
				"LZ77",
				"OpenDoc",
				"SafeDisk",
				"TypeConfig",
				"UPXShell",
				"UsbDoc",
				"UsbExe"
			],
			"source_id": "ETDA",
			"reports": null
		}
	],
	"ts_created_at": 1775434935,
	"ts_updated_at": 1775826773,
	"ts_creation_date": 0,
	"ts_modification_date": 0,
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