Detection rules › Sigma

Potential Webshell Creation On Static Website

Severity
medium
Author
Beyu Denis, oscd.community, Tim Shelton, Thurein Oo
Source
upstream

Detects the creation of files with certain extensions on a static web site. This can be indicative of potential uploads of a web shell.

MITRE ATT&CK coverage

TacticTechniques
PersistenceT1505.003 Server Software Component: Web Shell

Event coverage

ProviderEvent IDTitle
Sysmon11FileCreate

Stages and Predicates

Stage 1: all of selection_wwwroot_path

TargetFilename|contains: '\inetpub\wwwroot\'

Stage 2: all of selection_wwwroot_ext

or:
TargetFilename|contains: .ashx
TargetFilename|contains: .asp
TargetFilename|contains: .ph
TargetFilename|contains: .soap

Stage 3: all of selection_htdocs_path

or:
TargetFilename|contains: '\htdocs\'
TargetFilename|contains: '\html\'
TargetFilename|contains: '\www\'

Stage 4: all of selection_htdocs_ext

TargetFilename|contains: .ph

Stage 5: not 1 of filter_main_*

or:
Image: System
TargetFilename|contains: '\AppData\Local\Temp\'
TargetFilename|contains: '\Windows\Temp\'
TargetFilename|contains: '\xampp'

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
Imageeq
  • System corpus 8 (sigma 8)
TargetFilenamematch
  • .ashx
  • .asp
  • .ph
  • .soap
  • \AppData\Local\Temp\ corpus 11 (sigma 11)
  • \Windows\Temp\ corpus 3 (sigma 3)
  • \htdocs\
  • \html\
  • \inetpub\wwwroot\ corpus 2 (sigma 2)
  • \www\
  • \xampp