SECURITY: Basic OS Security (en)

Disable Services

• Disable Remote Desktop
• Check active ports

 nmap -sT -O localhost
 netstat -tulpn
 netstat -ntlupa

• Check daemons, in Ubuntu, you can use:

 apt-get install sysv-rc-conf
 sysv-rc-conf --list | grep '3:on'

 service serviceName stop
 sysv-rc-conf serviceName off

Alternative interesting commands:

 sysv-rc-conf apache2 on
 sysv-rc-conf --list apache2

Other alternative commands:

 update-rc.d <service> defaults
 update-rc.d <service> start 20 3 4 5
 update-rc.d -f <service> remove

Files Security

• File Permission

 chmod

• File Owner

 chown

• File Encryption

• Hard Disk Partition

 df -h   ensure separate partition

• Find World Writable files

 find / -xdev -type d \( -perm -0002 -a ! -perm -1000 \) -print

• Find No owner files

 find / -xdev \( -nouser -o -nogroup \) -print

File Transfer

• Disable FTP

 /etc/init.d/ftp stop
 iptables block

• Habitually use SCP

 scp

Sharing Files

• Enable / Disable SMB

 /etc/init.d/smbd stop
 iptables block

Password

User Account and Strong Password Policy

• Password Age
• Force Password Change
• Restrictions on Using Old Passwords
• Lock User Accounts after Several Failed Logins
• Verify No Accounts with Empty Passwords?
• Ensure No Non-Root Accounts Have UID 0

Read 20 Linux Server Hardening Security Tips