UNC4841 - SSL Certificate Exfiltration Via Openssl

 1title: UNC4841 - SSL Certificate Exfiltration Via Openssl
 2id: 60911c07-f989-4362-84af-c609828ef829
 3status: test
 4description: Detects the execution of "openssl" to connect to an IP address. This techniques was used by UNC4841 to exfiltrate SSL certificates and as a C2 channel with named pipes. Investigate commands executed in the temporal vicinity of this command.
 5references:
 6    - https://www.mandiant.com/resources/blog/barracuda-esg-exploited-globally
 7author: Nasreddine Bencherchali (Nextron Systems)
 8date: 2023/06/16
 9tags:
10    - attack.defense_evasion
11    - attack.t1140
12    - detection.emerging_threats
13logsource:
14    product: linux
15    category: process_creation
16detection:
17    selection:
18        Image|endswith: '/openssl'
19        CommandLine|re: '[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}'
20        CommandLine|contains|all:
21            - 's_client'
22            - '-quiet'
23            - '-connect'
24        CommandLine|contains:
25            - ':443'
26            - ':8080'
27    condition: selection
28falsepositives:
29    - Unknown
30level: high