Suspicious Excel Outbound Network Connection

ATT&CK techniques

Priv Esc → C2

Recon
Resource Dev
Initial Access
Execution
Persistence
Priv Esc
- T1055Process Injection
Defense Evasion
- T1055Process Injection
Cred Access
Discovery
Lateral Movement
Collection
C2
- T1071.001Web Protocols
Exfiltration
Impact

What it detects

This rule detects Excel.exe initiating an outbound network connection, which is unusual for a spreadsheet application that has no child process. In the WithSecure Initial Access Lab 4 an Excel 4.0 SLK macro injects meterpreter shellcode into Excel itself which then beacons over HTTPS to a non-Microsoft address. Attackers keep the malicious code inside the Office host to avoid spawning a suspicious child process.

Reporting behind it

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Suspicious Excel Outbound Network Connection

Pivot detection · T1071.001 · 9 related

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.

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