RSA warned customers last month of a security breach that may have compromised its SecurID two-factor authentication system, which is widely used by banks around the world to protect their internal and customer-facing online banking systems.

In a blog post on the company's Web site, Finextra contributor Uri Rivner says the breach arose after an employee retrieved an e-mail from their junk folder entitled "2011 Recruitment Plan" and opened an attached excel file.

The excel spreadsheet contained a zero-day exploit that installs a backdoor through an Adobe Flash vulnerability that has now been patched.

The attacker then used a remote administration tool known as Poison Ivy RAT variant to enable them to control the machine. From there, the attacker first harvested access credentials - domain admin, and service accounts - from the compromised users.

"They performed privilege escalation on non-administrative users in the targeted systems, and then moved on to gain access to key high value targets, which included process experts and IT and Non-IT specific server administrators," says Rivner.

The final stage of the hack saw the crooks go into servers of interest, remove data and move it to internal staging servers where it was aggregated, compressed and encrypted for extraction. FTP was used to transfer many password protected RAR files from the RSA file server to an outside staging server.

Says Rivner: "At RSA we're already learning fast, making both small-term hardening moves and giant strides towards establishing a whole new defense doctrine. We're implementing techniques that just a couple of weeks ago I thought were in the realm of long-term roadmaps."

In a possibly related move, RSA partent company EMC has acquired Virginia-based NetWitness Corporation, a provider of network security monitoring and analysis software. NetWitness will operate as part of RSA, "providing real-time visibility into network activity and adding efficiency to incident investigations and workflow".