Mail Protocols

Detection of Mail Protocol-Based C2 Activity (SMTP, IMAP, POP3)

Filter Network Traffic: Employ network appliances and endpoint software to filter ingress, egress, and lateral network traffic. This includes protocol-based filtering, enforcing firewall rules, and blocking or restricting traffic based on predefined conditions to limit adversary movement and data exfiltration. This mitigation can be implemented through the following measures:

Ingress Traffic Filtering:

• Use Case: Configure network firewalls to allow traffic only from authorized IP addresses to public-facing servers.
• Implementation: Limit SSH (port 22) and RDP (port 3389) traffic to specific IP ranges.

Egress Traffic Filtering:

• Use Case: Use firewalls or endpoint security software to block unauthorized outbound traffic to prevent data exfiltration and command-and-control (C2) communications.
• Implementation: Block outbound traffic to known malicious IPs or regions where communication is unexpected.

Protocol-Based Filtering:

• Use Case: Restrict the use of specific protocols that are commonly abused by adversaries, such as SMB, RPC, or Telnet, based on business needs.
• Implementation: Disable SMBv1 on endpoints to prevent exploits like EternalBlue.

Network Segmentation:

• Use Case: Create network segments for critical systems and restrict communication between segments unless explicitly authorized.
• Implementation: Implement VLANs to isolate IoT devices or guest networks from core business systems.

Application Layer Filtering:

• Use Case: Use proxy servers or Web Application Firewalls (WAFs) to inspect and block malicious HTTP/S traffic.
• Implementation: Configure a WAF to block SQL injection attempts or other web application exploitation techniques.

Network Intrusion Prevention: Use intrusion detection signatures to block traffic at network boundaries.