An effective strategy for mitigating attacks involves explicitly permitting only specific types of traffic through a firewall. Services such as Domain Name System (DNS), Simple Mail Transfer Protocol (SMTP), and File Transfer Protocol (FTP) are commonly allowed. Additionally, remote access for administrators is often configured, allowing protocols like Secure Shell (SSH), syslog, and Simple Network Management Protocol (SNMP).
While these services are essential, they should be controlled and monitored to prevent security vulnerabilities, as exploitation of these services can lead to significant risks.