File Download From IP Based URL Via CertOC.EXE

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

Detects when a user downloads a file from an IP based URL using CertOC.exe

MITRE ATT&CK coverage

Tactic	Techniques
Command & Control	`T1105` Ingress Tool Transfer

Event coverage

Provider	Event ID	Title
Sysmon	1	Process creation

Stages and Predicates

Stage 1: `all of selection_img`

or:
Image|endswith: '\certoc.exe'
OriginalFileName: CertOC.exe

Stage 2: `all of selection_ip`

CommandLine|re: '://[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}'

Stage 3: `all of selection_cli`

CommandLine|contains: -GetCACAPS

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	`-GetCACAPS` corpus 2 (sigma 2)
`CommandLine`	regex_match	`://[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}` corpus 5 (sigma 5)
`Image`	ends_with	`\certoc.exe` corpus 10 (sigma 10)
`OriginalFileName`	eq	`CertOC.exe` corpus 6 (sigma 6)