The recommendations included configuring recursive DNS resolvers to only be accessible from the organization's networks, enforcing query rate limits for authoritative DNS servers that do need to be queried from external networks and to implement the anti-spoofing network filtering methods defined in IETF's Best Current Practice (BCP) 38 document.
It's admirable that REN-ISAC is taking this step of notifying its members and educating them about this problem, said Roland Dobbins, a senior analyst in the security engineering and response team at DDoS mitigation vendor Arbor Networks. Other industry associations should do so as well, he said.
By their nature, academic institutions tend to be more open with their access policies and haven't necessarily hardened everything to a degree that would ensure their servers can't be abused, Dobbins said. Arbor has seen open DNS resolvers on all kinds of networks including educational ones, that were used to launch DNS reflection attacks, he said.
However, it's important to understand that DNS reflection attacks are only one type of amplification attack, Dobbins said. Other protocols including SNMP (Simple Network Management Protocol) and NTP (Network Time Protocol) can be abused in a similar way, he said.
Securing and properly configuring DNS servers is important, but it's even more important to implement BCP 38, Dobbins said. Anti-spoofing should be applied on all Internet-facing networks so that spoofed packets cannot originate from them. "The closer we get to universal application of BCP 38, the harder it becomes for attackers to launch DDoS amplification attacks of any kind."