In accordance with the MITRE ATT & CK mapping utilized by FortiSIEM 7.3 and FortiSOAR 7.6 , the described behaviors correspond to the following techniques:

Non-Standard Port (T1571): This technique involves adversaries communicating using a protocol and port pairing that are typically not associated. The incident report identifies HTTPS (TLS) traffic running on TCP 8443 rather than the standard port 443. FortiSIEM specifically includes built-in correlation rules, such as " Suspicious Typical Malware Back Connect Ports, " designed to detect these protocol-port mismatches.

Exfiltration Over Alternative Protocol (T1048): This technique describes adversaries stealing data by exfiltrating it over a different protocol than the primary command and control (C2) channel. In this scenario, while the C2 channel is established via HTTPS on port 8443, the adversary is transferring staged files using DNS queries with oversized TXT payloads . DNS is a common " alternative protocol " used to bypass standard data transfer monitoring and egress filtering.

Analysis of Incorrect Options:

Exploitation of Remote Services (B): This technique falls under Initial Access or Lateral Movement tactics, focusing on gaining entry into a system via vulnerabilities in network services like SMB or RDP. It does not apply to the maintenance of an established C2 channel or the exfiltration of data.

Hide Artifacts (D): This is a Defense Evasion technique where an adversary attempts to conceal their presence by removing traces such as log files or registry keys. While the attacker is " imitating normal traffic, " the specific acts of using a non-standard port and DNS exfiltration are primary behavioral signatures defined by their own more specific techniques.