Unwanted Malicious Script

Before few months ago, I got a call regarding Internet trouble. They had troubled opening Internet. They could easily access first page of any website but they couldn't reach second pages or other links of visited website. I checked everywhere and found few viruses and deleted them. But, after then system couldn't let me access Internet. Suddenly, I found installed malicious script on that machine with Yahoo! logo. (Please check following screen shot)


I removed that malicious script from add/remove program options. Restart that machine and it started working normally. They used Yahoo messenger and accept/invite people to share file/web cam. Thus they got said malicious script.

Countermeasures:
(1) Do not accept / invite any one for photo/file sharing or web cam whom you really don't know because it establishes direct connection.
(2) Be careful in Yahoo chat rooms because there are so many fake id users whom will inject any malicious script forcefully via direct connection as per No(1)
(3) Don't click any URL shown in Yahoo chat room's window or your buddy's chat window.
(4) If possible create a fake id for chatting other than your email id.
(5) Always use strong password for security.
(6) Install a good anti virus software and update it on regular basis.

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