Phishers only need to land a minute percentage of victims to make scams worthwhile.

Stats culled from Trusteer's anti-phishing browser plug-in, which is offered by banks to their clients as a transaction security add-on, revealed that 0.47 per cent of a bank’s customers fall victim to phishing attacks each year. The figure comes from the number of users who visited and attempted to enter data onto a known phishing site but escaped because they were using Trusteer's Rapport browser security plug-in.

Half (45 per cent) of bank customers who are redirected towards a phishing site attempted to hand over their login credentials.

The overall response rate to phishing scams translates to between $2.4m-$9.4m in annual fraud losses (per one million online banking clients), according to Trusteer.

Trusteer's report (PDF) is worth considering because it looks at how many would-be marks respond to phishing emails (ie live attack data). Most surveys only look at how many phishing attacks are launched and what brands are targeted, without considering how successful these attacks actually might be.

The security software firm has come to prominence this year after signing up many banks, including NatWest and Alliance & Leicester in the UK, as customers of its transaction security software. Trusteer obviously has a vested interest in talking up the financial losses and danger posed by phishing but that doesn't mean it's necessarily wrong.

Harvesting online bank login credentials before cashing out compromised accounts is a major activity in the underground economy, which is growing more sophisticated and mature. The market has grown to the point where hackers have developed tools to harvest data from phishers, a sort of virtual stick-up.

The cyber equivalent of The Wire's Omar Little have developed an auto-whaling tool designed to harvest logins stored on phishing sites. Such attacks are possible because crooks themselves are making website security errors, as a blog post by FaceTime security researcher Chris Boyd explains. ®