Hey HarumaN, I guess your off line now. It's probably a Trogan from a porn site like RayB said, one of those dialers. If your using Win2000 or XP go to this site
http://www.techspot.com/tweaks/win2k_services/index.shtml it will show you what Services to disable to prevent security problems, etc. Turn off Java whenever possible when surfing and disable Cookies and don't forget to clean your cache. Like Peale said, Avoid Internet Explorer, personally I use FireFox.
This is what I normally do to find what viruse/s are my on 2000 and XP machines...
1. Do a Google search. Try different keywords to search your problem. Usually works for me. Check out Nortons site for known virus threats. If it doesn't work try step 2...
2. Run Task Manager and disable any process that looks out of place. Windows won't let you close critical processes so you should be alright closing processes that look weird. Make a list of the Image Names and do a search on the net if you are wondering what they are. Take note of what processes are running and open your internet conection. If you still have the problem go back to the Task Manager and take note of the new processes now running. Then do a google search on the new processes to determine the exact virus threat and treat it accordingly. If your Internet conection is fine then you closed the problem process/es. Again do a search (first lot you took note off) to find out what your processes are doing. This helps narrow down the problem. This step usually works for me, becouse most viruses, not all, run in memory and are usually listed in the Task Manager.
NOTE: Some Viruses in memory stay there even after you Reboot your computer, so sometimes a cold boot (turn comp off) to clear memory is the best.
Sounds like alot of work, but it's better than formatting and reinstalling all your software and prefs. If this doesn't do it try step 3...
3. Run MSCONFIG and in the System Configuration Utility go to Startup and Disable the Startup Items listed (any that you know are ok leave them enabled) and click OK. You can enable them later if needed. In Win2000 you will need to get this file
http://www.techadvice.cc/files/s29k2/win-xp/msconfig.exeand saving it to c:\windows\system32 (obviously \windows being whatever your windows directory is) to run MSCONFIG.
NOTE: If your comp won't boot after, then go into the boot options F8 (on some machines) and start in safe mode and repeat step 3 but enable anything that needs to run, although you shouldn't have to. I had that happen to me once.
Hopefully by now you have identified and cleaned the Virus, if it is a virus, it may be a bad modem, conflicting modem settings or even problems with your provider. I'm leaning towards the virus.
If you haven't cleaned out the virus yet, you can update your virus software and run a virus scan, load the programs listed in this thread (they are all great utilities) and run scans. Go to Add and Remove Software and remove any suspicious software. Run a search of your Hard Drive using known keywords like dial, dialer, etc. and use the wildcard * if needed.
Here's a couple of things to try, asuming it's not a virus.
Uninstall the modem software and delete the modem drivers then cold boot your comp and reinstal the modem software and drivers and finally setup your account again and try it.
Check your modem manufacturer for updates.
Check for security and driver updates for your OS.
Call your provider and ask if anyone else has had a similar problem, perhaps they may know something.
I know this is a long response, forgive me if I've put you asleep, but I hope some of this helps...