I did some online trades with my credit card in this pc where we removed these malwares after the Malicious URLs menssages started to show, believing Avast was giving enough protection.
There is no antivirus product with 100% detection rate of the world wide malware. Antivirus works at the level of the signature and at known heuristic detection.
You had worm infection. That's why I recommend you MCShield program, becose s.k "USB Guardian" and other "USB AntiVirus" doesn't provide sufficient protection.
http://www.microsoft.com/security/portal/threat/encyclopedia/entry.aspx?Name=Worm%3AWin32%2FVobfus.QYou're had on your computer installed adware too. Adware is program whose role is to forcing advertising material and final goal is earning.
AntiVirus will not prevent installation of adware for several reasons. Let's put it this way:
- adware isn't characterized as malicious software (malware)
- you have allowed adware installation (unwittingly, but you did allowed)
- you accept the terms and conditions of the license when installing some adware ( standalone or via program )
- adware is warned you about URL and for change attempt on home page, and you did allow that action.
- adware has its own uninstaller, and only can be characterized as a PUP (Potentially Unwanted Programs)
- avast have browser cleanup tool, integrated in avast, designed to remove for them known adwares.
Should I be worried? Its reccomended to contact my credit company and request another credit card number?
I do recommend that, Yes.