Potential Persistence Via Custom Protocol Handler

Severity: medium
Author: Nasreddine Bencherchali (Nextron Systems)
Source: upstream

Detects potential persistence activity via the registering of a new custom protocole handlers. While legitimate applications register protocole handlers often times during installation. And attacker can abuse this by setting a custom handler to be used as a persistence mechanism.

MITRE ATT&CK coverage

Tactic	Techniques
Persistence	`T1112` Modify Registry
Defense Evasion	`T1112` Modify Registry

Event coverage

Provider	Event ID	Title
Sysmon	13	RegistryEvent (Value Set)

Stages and Predicates

Stage 1: `selection`

Details|startswith: 'URL:'
TargetObject|startswith: 'HKCR\'

Stage 2: `not 1 of filter_main_*`

or:
Details|startswith: 'URL:ms-'
Image|startswith: 'C:\Program Files (x86)'
Image|startswith: 'C:\Program Files\'
Image|startswith: 'C:\Windows\SysWOW64\'
Image|startswith: 'C:\Windows\System32\'

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
`Details`	starts_with	`URL:` `URL:ms-`
`Image`	starts_with	`C:\Program Files (x86)` `C:\Program Files\` corpus 15 (sigma 15) `C:\Windows\SysWOW64\` corpus 16 (sigma 16) `C:\Windows\System32\` corpus 16 (sigma 16)
`TargetObject`	starts_with	`HKCR\`