Safari and Chrome affected by Torrents

So, my friend recently downloaded a bunch of torrent related stuff onto my mac with the aspirations of watching a movie. When I went to use my comp the next day, my search engines were acting strange. The safari toolbar had been changed and had a ebay and amazon button that were new to me. The search engine was changed from google to yahoo! and further more facebook refuses to connect to safari. I have chrome too and all of these changes were the same except for facebook, which works on chrome. I really am not sure what happened but I know that something is different. On chrome, even though I've switched it back to google, If i search in a new tab it will search in yahoo. Can any wise mac gurus shed any light as to what is going on here? I'm pretty sure some funky thing was installed on my comp, I just dunno what it is.

Answer

It is possible that some malware was installed as a part of installing other software.

You could start by downloading and installing ClamAV -- an free antivirus application for the Mac. Have it scan your entire hard drive.

You might also take a look at Safari > Preferences > Extensions and then investigate what each of those extensions is. Often when browser behavior is modified by a software installation, extensions were installed into those browsers. If you find an extension that is suspect, it's possible there are other files elsewhere on your system related to the malware that was installed. Through an Internet search, you should be able to find steps to remove any installed malware and restore your settings back to normal.