Leading UK banks have been targeted by online criminals who used Storm botnets to unleash phishing attacks.

The attacks could mark the emergence of a new threat from the Storm botnet, according to a report from security company RSA's Anti-Fraud Command Center (AFCC).

UK financial institutions were the second most targeted in the world last month, accounting for 15 percent of global banking brands targeted, behind the US with 61 percent.

Attackers used the Storm botnet as a fast flux-network, frequently rotating the IP address of the infected computers sending out the phishing content, making them much more difficult to track down.

RSA analysts warn the Storm botnet could now be used as the infrastructure behind a new surge of fast-flux phishing attacks.