Potential Credential Dumping Activity Via LSASS

Severity: medium
Author: Samir Bousseaden, Michael Haag
Source: upstream

Detects process access requests to the LSASS process with specific call trace calls and access masks. This behaviour is expressed by many credential dumping tools such as Mimikatz, NanoDump, Invoke-Mimikatz, Procdump and even the Taskmgr dumping feature.

MITRE ATT&CK coverage

Tactic	Techniques
Credential Access	`T1003.001` OS Credential Dumping: LSASS Memory

Event coverage

Provider	Event ID	Title
Sysmon	10	ProcessAccess

Stages and Predicates

Stage 1: `selection`

or:
CallTrace|contains: dbgcore.dll
CallTrace|contains: dbghelp.dll
CallTrace|contains: kernel32.dll
CallTrace|contains: kernelbase.dll
CallTrace|contains: ntdll.dll
or:
GrantedAccess|contains: 0x1038
GrantedAccess|contains: 0x1438
GrantedAccess|contains: 0x143a
GrantedAccess|contains: 0x1fffff
TargetImage|endswith: '\lsass.exe'

Stage 2: `not 1 of filter_main_system_user`

or:
SourceUser|contains: AUTHORI
SourceUser|contains: AUTORI

Stage 3: `not 1 of filter_optional_*`

or:
CallTrace|contains: ':\Windows\Temp\asgard2-agent\'
CallTrace|contains: '\thor\thor64.exe+'
CallTrace|contains: '|UNKNOWN('
GrantedAccess: 0x103800
SourceImage|endswith: ':\Windows\Sysmon64.exe'

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
`CallTrace`	match	`:\Windows\Temp\asgard2-agent\` `\thor\thor64.exe+` `dbgcore.dll` corpus 2 (sigma 2) `dbghelp.dll` corpus 2 (sigma 2) `kernel32.dll` `kernelbase.dll` `ntdll.dll` `\|UNKNOWN(` corpus 2 (sigma 2)
`GrantedAccess`	eq	`0x103800`
`GrantedAccess`	match	`0x1038` `0x1438` `0x143a` `0x1fffff`
`SourceImage`	ends_with	`:\Windows\Sysmon64.exe`
`SourceUser`	match	`AUTHORI` `AUTORI`
`TargetImage`	ends_with	`\lsass.exe` corpus 13 (sigma 13)

Neighbors

Broader alternatives (more inclusive than this rule)

These rules match a superset of what this rule catches. They cover the same events plus more. Use them if you want wider coverage and can absorb more false positives.

Potentially Suspicious GrantedAccess Flags On LSASS [sigma] (drops 2 filters this rule applies) (first-stage match only; downstream stages may differ)