Process Access via TrolleyExpress Exclusion

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

Detects a possible process memory dump that uses the white-listed Citrix TrolleyExpress.exe filename as a way to dump the lsass process memory

MITRE ATT&CK coverage

Tactic	Techniques
Defense Evasion	`T1218.011` System Binary Proxy Execution: Rundll32
Credential Access	`T1003.001` OS Credential Dumping: LSASS Memory

Event coverage

Provider	Event ID	Title
Sysmon	1	Process creation

Stages and Predicates

Stage 1: `selection`

or:
CommandLine|contains: '\TrolleyExpress 7'
CommandLine|contains: '\TrolleyExpress 8'
CommandLine|contains: '\TrolleyExpress 9'
CommandLine|contains: '\TrolleyExpress.exe -ma '
CommandLine|contains: '\TrolleyExpress.exe 7'
CommandLine|contains: '\TrolleyExpress.exe 8'
CommandLine|contains: '\TrolleyExpress.exe 9'

Stage 2: `renamed`

Image|endswith: '\TrolleyExpress.exe'

Stage 3: `not 1 of filter*`

or:
OriginalFileName: null
OriginalFileName|contains: CtxInstall

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	`\TrolleyExpress 7` `\TrolleyExpress 8` `\TrolleyExpress 9` `\TrolleyExpress.exe -ma` `\TrolleyExpress.exe 7` `\TrolleyExpress.exe 8` `\TrolleyExpress.exe 9`
`Image`	ends_with	`\TrolleyExpress.exe` corpus 2 (sigma 2)
`OriginalFileName`	match	`CtxInstall`