Dialers 

A dialer is a little computer program. Dialers build a connection to the Internet or some network using telephone or ISDN network. They reconfigurate default dial-in number to much more expensive one. They have the ability to run in the background, hiding their presence. This is threat for those who have a computer with modem dial-in. The result of dialer work might be very expensive.
There are dialers that are necessary for user’s computer because they are used to connect to the Internet, but there are also those dialers that are in list of malware. “Bad” dialers use security holes and most often in Microsoft’s operating systems. Using security holes dialers change dial-in configuration.
Dialers that are used for Internet connection provide cheap service, but those that use 900 number or FTP site to dial out and a user can be charged up to fantastic sums of money. In fact using 900 number most of dialers make money.
Dialers’ targets are users that use modem. Users with DSL connection are almost not affected. Maybe dialers are downloaded and installed but they don’t work in DSL network. Except when ISDN adapter is installed, because then dialer will need a connection.
“Bad” dialers can be identified. For example when you’re surfing on the Internet and a download dialog opens, there would be a small hint about price of service, or it would be written that the service is free. Do not trust that kind of information. Most of malicious dialers use it. Then you even will not be able to determine download, because “Cancel” accepts download. After the dialer installs it becomes a default connection although you didn’t set it. Every action the dialer does is done without your knowledge. No information about prices or false information before dialing. No uninstall file or function is provided. This situation makes a lot of problems and costs a lot.
Is there any protection or prevention? Yes there is.

• Do not open spam e-mails and links in those e-mails. Especially when e-mail contains information about anti-virus program or site,which you don’t even use.
• Turn off the Windows Messenger service.
• The dialing number should be regularly checked.
• User must have a good and trustful anti-virus and anti-spyware program, which could block ActiveX script.
• There are also softwares called a² and stopITnow!. They detect and blocks dialers immediately they start running.
• Update regularly your operating system.
• Be careful if you’re using CAPI-port or USB-port.
• Use routers.
• SAT-connections offers some protection from malicious dialers.
• If you suspect that you’ve become a victim of malicious dialer – do not pay the phone bill for long distance service and report about it to your Internet provider.
• And you have an opportunity to block long distance service.