Network Egress Filtering and the RSA SecurID Attack
Reading details about the recent attack and compromise at SecurID, I was dumbfounded when I came across the following:
“The attacker then used FTP to transfer many password protected RAR files from the RSA file server to an outside staging server at an external, compromised machine at a hosting provider. The files were subsequently pulled by the attacker and removed from the external compromised host to remove any traces of the attack.”
I’m not surprised at all that an attacker was able to infiltrate the RSA private network. However, with this and myriad similar attacks I’ve read about over the past few years, one thing that consistently amazes me is the relative ease with which attackers can get back out.
It appears in this case that RSA allows outbound FTP to anywhere on the Internet. Clearly this is not good security practice. This is not to say that an attacker couldn’t use another channel to exfiltrate stolen data, but having such generous outbound access rules for file transfer protocols makes it that much easier for the criminals.
To provide better protection from these types of attacks, security policy should be updated to disallow unrestricted outbound FTP access to the general Internet. Following the principle of least privilege, outbound FTP access should be granted only to certain users and to specific sites, and only after it is determined there is a business requirement for such access. This access should be reviewed on a periodic basis.
Using Forefront TMG 2010 and leveraging the TMG Firewall Client, it is possible to create outbound FTP access rules and enforce user and group authentication. Although this won’t necessarily prevent an attacker from uploading data through the gateway, it presents yet another hurdle for the attacker to clear in order to extract data. If the attacker is still successful, the access logs on the Forefront TMG firewall will include valuable forensic data, including the name of the application used to transfer data and the account information used by the attacker, in addition to the usual log detail (e.g. source and destination IP addresses, etc.).
State-of-the art perimeter defense technology is not enough. Security policy and strong network egress filtering are essential to prevent data loss. I’d suggest reviewing your outbound access policies today.