Kerberos Traffic from Unusual Process

## Triage and analysis

### Investigating Kerberos Traffic from Unusual Process

Kerberos is the default authentication protocol in Active Directory, designed to provide strong authentication for
client/server applications by using secret-key cryptography.

Domain-joined hosts usually perform Kerberos traffic using the `lsass.exe` process. This rule detects the occurrence of
traffic on the Kerberos port (88) by processes other than `lsass.exe` to detect the unusual request and usage of
Kerberos tickets.

#### Possible investigation steps

- Investigate the process execution chain (parent process tree) for unknown processes. Examine their executable files
for prevalence, whether they are located in expected locations, and if they are signed with valid digital signatures.
- Investigate other alerts associated with the user/host during the past 48 hours.
- Check if the Destination IP is related to a Domain Controller.
- Review event ID 4769 for suspicious ticket requests.
- Retrieve the process executable and determine if it is malicious:
  - Use a private sandboxed malware analysis system to perform analysis.
    - Observe and collect information about the following activities:
      - Attempts to contact external domains and addresses.
      - File and registry access, modification, and creation activities.
      - Service creation and launch activities.
      - Scheduled task creation.
  - Use the PowerShell Get-FileHash cmdlet to get the files' SHA-256 hash values.
    - Search for the existence and reputation of the hashes in resources like VirusTotal, Hybrid-Analysis, CISCO Talos, Any.run, etc.

### False positive analysis

- This rule uses a Kerberos-related port but does not identify the protocol used on that port. HTTP traffic on a
non-standard port or destination IP address unrelated to Domain controllers can create false positives.
- Exceptions can be added for noisy/frequent connections.

### Response and remediation

- Initiate the incident response process based on the outcome of the triage.
- Isolate the involved host to prevent further post-compromise behavior.
- Investigate credential exposure on systems compromised or used by the attacker to ensure all compromised accounts are
identified. Reset passwords for these accounts and other potentially compromised credentials, such as email, business
systems, and web services.
  - Ticket requests can be used to investigate potentially compromised accounts.
- If the triage identified malware, search the environment for additional compromised hosts.
  - Implement temporary network rules, procedures, and segmentation to contain the malware.
  - Stop suspicious processes.
  - Immediately block the identified indicators of compromise (IoCs).
  - Inspect the affected systems for additional malware backdoors like reverse shells, reverse proxies, or droppers that
  attackers could use to reinfect the system.
- Remove and block malicious artifacts identified during triage.
- Run a full antimalware scan. This may reveal additional artifacts left in the system, persistence mechanisms, and
malware components.
- Determine the initial vector abused by the attacker and take action to prevent reinfection through the same vector.
- Using the incident response data, update logging and audit policies to improve the mean time to detect (MTTD) and the
mean time to respond (MTTR).