Botnets and phising

A recent post to the Dailydave mailing list, titled Distributed Phishing, described an incident similar to the report we received yesterday. The report outlined a large organization's battle against a botnet that implemented a phishing attack against the organization's customers. The trend to use bots for hosting phishing websites on compromised systems is not new, and was documented in the Register article titled Phishers Tapping Botnets to Automate Attacks. Using bots in this manner makes it difficult to shut down the malicious site, because the attacker can quickly modify the domain record to point to another compromised system. One way to defend against such attacks is to work with the company hosting the DNS server that resolves the malicious domain name to remove or modify the offending records.

Attacks that we're observing now are becoming more elaborate. In the most recent report, the attacker was using a botnet to host not only the malicious websites, but also the DNS servers that provided domain resolution services for the targeted domain name. This setup allowed the attacker to move to a new DNS server when one of the malicious servers got shut down. An organization battling this threat typically has to deal with the registrar of the malicious domain, instead of attempting to shut down the individual DNS server. Unfortunately, many domain registrars don't have formal procedures for dealing with such requests, which makes it difficult for organizations to defend against such attacks.

Some ISP can help their customers combat such attacks by implementing a type of domain hijacking, intercepting and redirecting malicious DNS traffic that traverses their network. While this approach does not entirely mitigate the issue, it does mitigate it within the ISP's network; it is particularly effective if implemented by a large ISP. Considering the limitations of this mechanism, having domain registrars develop processes for addressing this attack scenario would be very helpful.