Phishing can be combined with other scams, and the US-CERT recommends that learning to identify fake antivirus could help stop an ongoing attack. Rogue antivirus is difficult to terminate. It causes realistic security warnings that ultimately request credit-card and personal information claiming that it will identify threats and remove them from the system. One recent scam involved a follow-up phone call from an attacker call center requesting access to the infected machine. The threat of being infected can be reduced significantly by actively maintaining and keeping your antivirus up to date, say security experts. The US-CERT recommends that users visit a vendor website directly when purchasing or renewing software subscriptions.