Detection rules › Sigma

Suspicious File Creation In Uncommon AppData Folder

Severity
high
Author
Nasreddine Bencherchali (Nextron Systems)
Source
upstream

Detects the creation of suspicious files and folders inside the user's AppData folder but not inside any of the common and well known directories (Local, Romaing, LocalLow). This method could be used as a method to bypass detection who exclude the AppData folder in fear of FPs

Event coverage

ProviderEvent IDTitle
Sysmon11FileCreate

Stages and Predicates

Stage 1: selection

or:
TargetFilename|endswith: .bat
TargetFilename|endswith: .cmd
TargetFilename|endswith: .cpl
TargetFilename|endswith: .dll
TargetFilename|endswith: .exe
TargetFilename|endswith: .hta
TargetFilename|endswith: .iso
TargetFilename|endswith: .lnk
TargetFilename|endswith: .msi
TargetFilename|endswith: .ps1
TargetFilename|endswith: .psm1
TargetFilename|endswith: .scr
TargetFilename|endswith: .vbe
TargetFilename|endswith: .vbs
TargetFilename|contains: '\AppData\'
TargetFilename|startswith: 'C:\Users\'

Stage 2: not filter_main

or:
TargetFilename|contains: '\AppData\LocalLow\'
TargetFilename|contains: '\AppData\Local\'
TargetFilename|contains: '\AppData\Roaming\'
TargetFilename|startswith: 'C:\Users\'

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.

FieldKindValues
TargetFilenameends_with
  • .bat corpus 15 (sigma 15)
  • .cmd corpus 8 (sigma 8)
  • .cpl corpus 2 (sigma 2)
  • .dll corpus 21 (sigma 21)
  • .exe corpus 18 (sigma 18)
  • .hta corpus 12 (sigma 12)
  • .iso corpus 5 (sigma 5)
  • .lnk corpus 5 (sigma 5)
  • .msi corpus 2 (sigma 2)
  • .ps1 corpus 15 (sigma 15)
  • .psm1 corpus 4 (sigma 4)
  • .scr corpus 8 (sigma 8)
  • .vbe corpus 13 (sigma 13)
  • .vbs corpus 16 (sigma 16)
TargetFilenamematch
  • \AppData\ corpus 3 (sigma 3)
  • \AppData\LocalLow\
  • \AppData\Local\ corpus 2 (sigma 2)
  • \AppData\Roaming\ corpus 2 (sigma 2)
TargetFilenamestarts_with
  • C:\Users\ corpus 12 (sigma 12)