Ubuntu: Up and Running

System Security

On the security side, because it was built from the ground up as a multiuser operating system, Ubuntu suffers far less from virus attacks, but they still must be guarded against. You also need to lock your computer against intrusion, whether via the Internet or from physical access to your hardware.

Passwords

Passwords are one of the most important parts of securing any computer. Unfortunately, most people don’t realize how easy it is these days for attackers to crack passwords based on dictionary words. In fact, even combinations of letters and numbers can be broken.

For example, one common way to save a password is to store it as a hash, which is a string of hexadecimal numbers derived from the original but which cannot be used to determine the password it came from—at least not in any practical timescale using current technology.

However, cunning hackers have spent years building huge databases of hashes for every password combination they can compute. These databases contain millions of combinations, so just imagine trying to think of an original combination of letters and numbers that won’t be in such a database. It would have to be quite long (probably in excess of 20 characters) to stand a chance of being unique.

So, not only can hackers send repeated guesses to a password prompt by running through their dictionaries of passwords, whenever they manage to compromise a weakly protected computer, they can gain access to the password files and also try hash dictionaries ...