Operating systems: windows, linux, macos, etc.
Networking: tcp/ip, dns, dhcp, routers, switches, firewalls, etc.
Programming languages: python, java, c++, javascript, etc.
Database management: mysql, oracle, microsoft sql server, mongodb, etc.
Cloud computing: amazon web services (aws), microsoft azure, google cloud platform (gcp), etc.
Cybersecurity: threat analysis, penetration testing, vulnerability assessment, etc.
Software development methodologies: agile, scrum, waterfall, etc.