- SafePay ransomware group
- Security-Enhanced Linux
- Security Information and Event Management
- Session Hijacking
- SHA1
- SideCopy
- SIM Swapping
- Smishing
- Smokeloader
- SNMP
- SOCKS
- SOHO Devices
- SPACEHOP
- SparkCat
- SparkKitty
- Spine Leaf Architecture
- Spoof
- SQL Injection
- SSH
- SSL
- Stateful Inspection
- Steganography
- Stingray
- Stream Cipher
- Subnet Mask