File With Suspicious Extension Downloaded Via Bitsadmin

Severity: high
Author: Florian Roth (Nextron Systems), Nasreddine Bencherchali (Nextron Systems)
Source: upstream

Detects usage of bitsadmin downloading a file with a suspicious extension

MITRE ATT&CK coverage

Tactic	Techniques
Persistence	`T1197` BITS Jobs
Defense Evasion	`T1036.003` Masquerading: Rename Legitimate Utilities, `T1197` BITS Jobs
Command & Control	`T1105` Ingress Tool Transfer

Event coverage

Provider	Event ID	Title
Sysmon	1	Process creation

Stages and Predicates

Stage 1: `all of selection_img`

or:
Image|endswith: '\bitsadmin.exe'
OriginalFileName: bitsadmin.exe

Stage 2: `all of selection_flags`

or:
CommandLine|contains: ' /addfile '
CommandLine|contains: ' /create '
CommandLine|contains: ' /transfer '

Stage 3: `all of selection_extension`

or:
CommandLine|contains: .7z
CommandLine|contains: .asax
CommandLine|contains: .ashx
CommandLine|contains: .asmx
CommandLine|contains: .asp
CommandLine|contains: .aspx
CommandLine|contains: .bat
CommandLine|contains: .cfm
CommandLine|contains: .cgi
CommandLine|contains: .chm
CommandLine|contains: .cmd
CommandLine|contains: .dll
CommandLine|contains: .gif
CommandLine|contains: .jpeg
CommandLine|contains: .jpg
CommandLine|contains: .jsp
CommandLine|contains: .jspx
CommandLine|contains: .log
CommandLine|contains: .png
CommandLine|contains: .ps1
CommandLine|contains: .psm1
CommandLine|contains: .rar
CommandLine|contains: .scf
CommandLine|contains: .sct
CommandLine|contains: .txt
CommandLine|contains: .vbe
CommandLine|contains: .vbs
CommandLine|contains: .war
CommandLine|contains: .wsf
CommandLine|contains: .wsh
CommandLine|contains: .xll
CommandLine|contains: .zip

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

Field	Kind	Values
`CommandLine`	match	`/addfile` corpus 5 (sigma 5) `/create` corpus 14 (sigma 14) `/transfer` corpus 5 (sigma 5) `.7z` corpus 2 (sigma 2) `.asax` `.ashx` `.asmx` `.asp` `.aspx` `.bat` corpus 8 (sigma 8) `.cfm` `.cgi` `.chm` corpus 2 (sigma 2) `.cmd` corpus 5 (sigma 5) `.dll` corpus 15 (sigma 15) `.gif` corpus 6 (sigma 6) `.jpeg` corpus 6 (sigma 6) `.jpg` corpus 7 (sigma 7) `.jsp` `.jspx` `.log` corpus 2 (sigma 2) `.png` corpus 7 (sigma 7) `.ps1` corpus 3 (sigma 3) `.psm1` `.rar` corpus 2 (sigma 2) `.scf` `.sct` `.txt` corpus 7 (sigma 7) `.vbe` corpus 4 (sigma 4) `.vbs` corpus 5 (sigma 5) `.war` `.wsf` corpus 2 (sigma 2) `.wsh` corpus 2 (sigma 2) `.xll` `.zip` corpus 4 (sigma 4)
`Image`	ends_with	`\bitsadmin.exe` corpus 23 (sigma 23)
`OriginalFileName`	eq	`bitsadmin.exe` corpus 9 (sigma 9)