White box testing Penetration testing and code reviews
Excellent Scripting/programming skills (e.g., C/C++, Perl, Python, Expect, tcpdump) to develop tools to conduct penetration testing
Good understanding of Security Concepts, common vulnerabilities and Fuzz testing
Good understanding of Security/Cryptography Algorithms
Familiarity with SELinux/AppArmor type tools
Network protocol knowledge i.e., TCP/IP, UDP, IPSEC, HTTP, HTTPS, DHCP/NTP etc.