Initial Access
Initial access encompasses the techniques adversaries use to gain their first foothold in a target environment. It is the first tactic in the MITRE ATT&CK framework and represents the critical entry point that all subsequent attack activities depend on.
Common Initial Access Techniques
Phishing (T1566)
Deceptive emails containing malicious attachments or links designed to deliver malware or harvest credentials. This remains the most common initial access vector.
Exploitation of Public-Facing Applications (T1190)
Attacking vulnerabilities in internet-facing systems — web servers, VPN appliances, email gateways, cloud services — to gain unauthorized access.
Valid Accounts (T1078)
Using stolen, purchased, or compromised credentials to authenticate legitimately to the environment through VPN, RDP, SSH, or cloud services.
Supply Chain Compromise (T1195)
Targeting software vendors, update mechanisms, or service providers to gain access to their customers' environments.
Drive-by Compromise (T1189)
Exploiting vulnerabilities in web browsers or plugins when victims visit compromised or malicious websites.
External Remote Services (T1133)
Exploiting or brute-forcing remote access services like VPN, RDP, or Citrix exposed to the internet.
Detecting Initial Access
- Monitor email security gateways for malicious attachments and URLs
- Track authentication anomalies (impossible travel, new devices, unusual times)
- Monitor internet-facing application logs for exploitation attempts
- Analyze VPN and remote access logs for unusual connection patterns
- Review third-party and vendor access for suspicious activity
Reducing Initial Access Risk
- Implement email authentication (SPF, DKIM, DMARC) and advanced filtering
- Promptly patch internet-facing systems
- Enforce multi-factor authentication on all external access
- Conduct regular attack surface discovery to identify exposed services
- Validate detection controls against each initial access technique
