2. Test your firewall

Posted on 12 May 2008 at 15:02

Ideally your firewall should be taking care of business by ensuring there are no open ports on your system. Hackers scan your PC for open ports and, unless your firewall is doing its job properly, they'll find you out.

Advanced port scanners such as those available at PC Flank (www.pcflank.com) will use various techniques such as TCP connect scanning and TCP SYN scanning to determine the status of all ports. You can also scan certain parts of the system, such as a typically vulnerable port or a specified range.

Stealth testing utilises a total of five scanning techniques to determine if your computer is visible to the wider internet: TCP ping, TCP NULL, TCP FIN, TCP XMAS and UDP scanning. The best known stealth scanner is the TruStealth Analysis tool at ShieldsUP (www.grc.com), which is recommended for self-scanning. This can very quickly see if any packets are returned to repeated pings (ICMP Echo Requests) - only perfectly stealthed machines with no ports showing are safe from hackers.

Jaime Lyndon A Janeza is the threat research projects manager with security vendor Trend Micro and uses ShieldsUP regularly. "It even works for mobiles," he says. "I tested it on my Nokia Communicator 9500. With all the new gadgets allowing for online browsing through various means, knowing that usage does not expose you to the nasties out there is certainly a good thing."

Internet ports are numbered from 1 to 65,535, but it's the first 1,023 that are reserved for incoming connections. Internet services and hacking applications listen on these ports. So a web server will listen on port 80, email servers on 25 and 110, and FTP servers on 21. ShieldsUP adds another 33 ports to its main scan to allow for other known problem areas with the Windows OS. If you want to know the full 65,535 port assignments you can do some bedtime reading at www.iana.org/assignments/port-numbers.

3. Exploit your PC

Hack it yourself

Author: Davey Winder