The number of beginning computer users has increased but their concern is mostly on the convenience of Internet and they don't put much emphasis on computer security. We receive increasing number of reports from users who encountered an unexpected problem when they downloaded programs from websites. The following is the example of problems that could happen as a result of careless download:

1. Your computer gets infected by computer virus.
2. You get connected to telephone service charged to the caller ('Dial Q2' in Japan) or overseas call unknowingly and receive an outrageous amount of telephone bill.
3. You lose documents on your hard drive.
4. Someone remotely controls your computer.
5. Someone steals or read your document on your hard drive.

There are other examples such as "web advertisement is added to outgoing emails" or "letters on the display are changed" etc. There are various types of malicious programs that pretends to be a good (convenient) program such as "speed up your download time" but the content is different from what it claims to be.

You never know what they can do to your computer once you execute these programs. It is difficult to know what is changed and how to uninstall such malicious programs.

After your computer is changed or destroyed, the only thing you can do is to format your hard drive and reinstall OS.

Most of the malicious programs are not virus but just simple software that anti-virus programs don't bother to detect. Therefore, you are not completely safe even though your anti-virus program doesn't detect any virus in the programs you download.

To try to avoid damage by malicious programs, always keep in mind that you should not download any programs except from the sites you can trust. Also ask yourself whether the program you are about to download is what you really want.  It is worth checking the digital signature of the program if there is.

When you are connected to the internet, you need to act on your own responsibility to avoid these problems.

Reference

• RFC 2504: Users' Security Handbook
• 3.1. The Dangers of Downloading