network security (all-IP), OS-security, IT early warning, attack detection, penetration testing, risk management, PKI, cryptography, critical infrastructure protection, security management, physical security, computer forensics, machine learning, malware-detection, –analysis and -defense, botnets, honeypots, VPN, IDS/IPS, backup/recovery, data center operation, server hardening, high availability (DRBD, heartbeat), monitoring, virtualization, storage systems, TCP/IP security, Linux, *BSD, Windows, Android, Java, C/C++, bash, perl, python, PHP, SQL, HTML, JavaScript, XML, Office, LaTeX