Corero Network Security has disclosed a significant new zero-day DDoS attack vector observed for the first time against its customers last week. The new technique is an amplification attack, which utilizes the Lightweight Directory Access Protocol (LDAP): one of the most widely used protocols for accessing username and password information in databases like Active Directory, which is integrated in most online servers.
While Corero’s team of DDoS mitigation experts has so far only observed a handful of short but extremely powerful attacks against their protected customers originating from this vector; the technique has potential to inflict significant damage by leveraging an amplification factor seen at a peak of as much as 55x. Therefore, in terms of its potential scale, if combined with the Internet of Things botnet that was utilized in the recent 655 Gigabyte attack against Brian Krebs’s website, we could soon see new records broken in the DDoS attack landscape, with potential to reach tens of Terabits per second in size in the not too distant future. The DDoS landscape has been extremely volatile in recent weeks, particularly with the release of the Mirai code and subsequent Mirai infected Internet of Things (IoT) devices, and we expect this trend to continue for the foreseeable future.
Dave Larson, CTO/COO at Corero Network Security, explains: “This new vector may represent a substantial escalation in the already dangerous DDoS landscape, with potential for events that will make recent attacks that have been making headlines seem small by comparison. When combined with other methods, particularly IoT botnets, we could soon see attacks reaching previously unimaginable scale, with far-reaching impact. Terabit scale attacks could soon become a common reality and could significantly impact the availability of the Internet– at least degrading it in certain regions.”
Reflection and amplification attacks
In this case, the attacker sends a simple query to a vulnerable reflector supporting the Connectionless LDAP service (CLDAP) and using address spoofing makes it appear to originate from the intended victim. The CLDAP service responds to the spoofed address, sending unwanted network traffic to the attacker’s intended target.
Amplification techniques allow bad actors to intensify the size of their attacks, because the responses generated by the LDAP servers are much larger than the attacker’s queries. In this case, the LDAP service responses are capable of reaching very high bandwidth and we have seen an average amplification factor of 46x and a peak of 55x.
Dave Larson explains: “LDAP is not the first, and will not be the last, protocol or service to be exploited in this fashion. Novel amplification attacks like this occur because there are so many open services on the Internet that will respond to spoofed record queries. However, a lot of these attacks could be eased by proper service provider hygiene, by correctly identifying spoofed IP addresses before these requests are admitted to the network. Specifically, following the best common practice, BCP 38, described in the Internet Engineering Task Force (IETF) RFC 2827, which describes router configurations that are designed to eliminate spoofed IP address usage by employing meaningful ingress filtering techniques, would reduce the overall problem of reflected DDoS by at least an order of magnitude.
“Today’s DDoS attacks are increasingly automated, meaning that attackers can switch vectors faster than any human can respond. The only effective defense against this type of DDoS attack vector requires automated mitigation techniques. Relying on out-of-band scrubbing DDoS protection to stop these attacks will cause significant collateral damage. Given the short duration and high volume attacks, legacy solutions simply cannot identify and properly mitigate in time to protect network availability.”
The CLDAP zero-day attacks targeted at Corero customers were automatically mitigated by the Corero SmartWall Threat Defense System with patented Smart Rule functionality. No human intervention was necessary in mitigating this previously unknown DDoS attack vector and no outages were caused as a result of these attacks in the Corero customer base, according to the company.