Connection to Commonly Abused Web Services

## Triage and analysis

### Investigating Connection to Commonly Abused Web Services

Adversaries may use an existing, legitimate external Web service as a means for relaying data to/from a compromised
system. Popular websites and social media acting as a mechanism for C2 may give a significant amount of cover due to the
likelihood that hosts within a network are already communicating with them prior to a compromise.

This rule looks for processes outside known legitimate program locations communicating with a list of services that can
be abused for exfiltration or command and control.

#### Possible investigation steps

- Investigate the script execution chain (parent process tree).
- Investigate other alerts related to the user/host in the last 48 hours.
- Verify whether the digital signature exists in the executable.
- Identify the kind of the operation (upload, download, tunneling, etc.).
- Use a sandboxed malware analysis system to perform analysis on the executable.
- Use the PowerShell Get-FileHash cmdlet to get the SHA-256 hash value of the file.
  - Search for the existence of this file in resources like VirusTotal, Hybrid-Analysis, CISCO Talos, Any.run, etc.

### False positive analysis

- This rule has a high chance to produce false positives because it detects communication with legitimate services. Noisy
false positives can be added as exceptions.

### 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.
- If the triage identified malware, search the environment for additional compromised hosts.
- Implement any temporary network rules, procedures, and segmentation required to contain the malware.