With the explosive growth in the number of computers and Internet use, the security problems of computers have attracted the interest of Internet users. In particular, the latest hacking attacks using DDoS (distributed denial-of-service) that hit major government and private Websites increased the concerns about network security. Although some media looked at the possibility that the attack may have been committed by North Korean hackers, it was not.

A DDoS attack is an attempt to make a computer resource unavailable by attacking a single target computer from multiple compromised systems. This is a major reason for service denial for users of the target system. That is, a large quantity of incoming messages (packets) causes the target system to shut down. Therefore, the attacked systems deny or give slow response to legitimate users.

A cracker, also called a hacker, indicates a person who breaks into the target system to damage it or to get illegitimate access to the resources. First, a cracker finds a defenseless computer to make it the DDoS master. Then, the intruder identifies and communicates with other systems that can be compromised. The intruder loads cracking tools through the Internet to multiple compromised systems. When people download some files from the Internet, cracking tools enter the computer. Finally, the intruder is able to control the infected computers (zombie PCs or agents) with a single simple command, and zombie PCs dispatch many flood attacks (packets) to a selected target. The overflow of packets causes denial of service.

How do you avoid being part of the attacking DDoS? Unfortunately, there are no effective ways to stop it, and we are exposed to becoming the victim of a DDoS attack, but there are methods which can reduce the likelihood that an attacker may use your computer to attack other computers.

- Check your computer has the newest anti-virus software
- Don’t install unconfirmed ActiveX files, and don’t download illegal files such as mp3,
- movie, or free software files.
- Don’t open doubtful attached files from your email
- Set up passwords for booting screens and operating systems to increase PC security
- Update your computer programs regularly

Now, ask yourself the following questions. Have you downloaded illegal files from unconfirmed Websites recently? Is your computer or Internet speed slower than usual? Does your computer have a booting problem? If your computer has one of the above symptoms, turn off the computer or modem and run vaccine programs in safety mode. If you change your bad habits in using the Internet and follow the above safety guidelines, you can protect your computers from viruses or cracking.