Throughout this chapter, we discussed security threats found at each of the OSI layers and saw how we can protect running services with a practical example.
Layer 1 attacks (mostly cable cuts) cannot be addressed with Linux.
Layer 2 attacks can be very disruptive as they can affect upper layer information.
Layer 3 attacks include packet sniffing, IP spoofing, and ICMP attacks.
Layer 4 attacks derived from TCP and UDP vulnerabilities include TCP SYN flooding, Land attacks, TCP connection hijacking, UDP floods, and Port scan attacks.
Layer 5, 6, and 7 attacks consist of attacks against different applications. We saw some advice on how to safely run DNS, CVS, Apache web server, Mail, OpenSSL, and SNMP services.
We gave an example on how to protect running services.