In the time it takes you to read this entry, two hackers will try to get into your computer.
The Hollywood stereotype of a hacker is a technically-savvy individual trying to get into a specific target computer - the spy trying to breach a military computer, the disgruntled employee vandalizing his former employer or the kid cracking a university system for bragging rights. In fact, most hackers today run brute force attacks using simple software-assisted techniques to randomly attack vast numbers of computers.
According to a Maryland Univ study, computers are attacked on average 2,244 times a day. That's an attack every 39 seconds.
Researchers in this study set up weak security on four computers with internet access, then recorded what happened as the individual machines were attacked. The vast majority of attacks came from relatively unsophisticated hackers using “dictionary scripts,” software that runs through lists of common usernames and passwords trying to break into a computer.
The most commonly guessed usernames were root, admin, test, guest, info, adm, mysql, user, administrator and oracle. The most common password-guessing technique was to use variations of the username. About 43 percent of all attempts simply reentered the username. The username followed by 123 was the second most-tried choice. Other common passwords included blank (that is, no password set), 123456, password, passwd, 123, test, asdf, qwerty and variations based on the date (such as January07).
Once hackers gain access to a computer, they set up back doors so they can easily regain access later, turning the target computer into part of their botnet which they will later either use directly or lease to other hackers so they can send out spam, attack yet more computers, run distributed denial of service attacks, etc.
Never use the kinds of usernames and passwords identified in this research. If your computer came with a default administrator or guest account, change the accountname immediately.
Always choose longer, less obvious passwords with combinations of upper and lowercase letters and numbers that are not as obvious to brute-force dictionary attacks. If your system can handle it, whole sentences make very strong passwords that are still easy to remember and to type.