Captchar.A is a Trojan horse that records keystrokes in order to collect captcha data, which may be used to generate accounts for legitimate Web sites.
Spyware Doctor can automatically remove the
Trojan. Even if you remove it manually, we recommend you should use Spyware Doctor to make sure it's completely removed from your system and will not be reinstalled by itself.
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Removal Instructions for Emerging Adware & Spyware