Security

File Security

•User-level protection•Protect personal files•Three ways of protection• password-based

• encryption-based

• access right

Password protection

•Login and password•Login names are public• /etc/passwd

•passwd

•yppasswd, nispasswd

Encryption

•Covert (encrypt) a file to a different form•Use gpg•gpg --gen-key• generates private & public keys

• ~/.gnupg

•encrypt & sign emails and files

System security

•Everyone is under threat•Specially when using Internet•Local threats also•Common sense, good practice•Err on the side of caution

Some threats

•Denial of Service (Dos)• Intrusion•Snooping•Viruses, Worms & Trojans•Rootkits

Initial steps to security

•shut down unwanted daemons• netstat -an

• /etc/services

•kill unwanted daemons• remove from init

•changing access permissions to needed services

Best Practices

•Complex passwords•Skip the root account•Don’t trust random binaries• strace, ltrace

•Log files• /var/log/syslog etc.

•Software update•Physical security

Firewall

•Packet filtering•Stateless / stateful filtering•netfilter / iptables•Firewall products• Firestarter, Smoothwall Express, IPCop, Shoreline