"Strong passwords are your first step in securing your systems. If a password can be easily guessed or compromised using a simple dictionary attack, your systems will be vulnerable to hackers, worms, Trojans, and viruses.
"Trojan, virus, and worm authors have had great success attacking systems with weak and/or default passwords. Take IRC/Flood Trojan for example. McAfee’s virus profile states that IRC/Flood has over 120 variants and has infected over 60,000 machines in the last 30 days. IRC/Flood succeeds by checking for 22 different different easy to guess admin passwords (variants vary). Unfortunately, there are a lot more where IRC/Flood came from, W32/Tzet.worm, W32/Random.worm, and W32.HLLW.Gaobot.gen are in the wild just to name three..."