In the vast landscape of cyber threats, a new player named Savvy Seahorse has emerged, showcasing a distinctive modus operandi that sets it apart from its counterparts. While the investment scam it orchestrates is unfortunately commonplace, it's the intricate infrastructure supporting it that demands attention.
Savvy Seahorse employs a sophisticated Traffic Distribution System (TDS), capitalizing on the Domain Name System (DNS) to perpetually alter its malicious domains, making takedowns a formidable challenge. This TDS, as detailed in a recent report by Infoblox, leverages Canonical Name (CNAME) records to maintain a fluid network of thousands of diverse domains.
Traditionally associated with HTTP-based TDS networks, the use of DNS in this context is a novel approach that poses unique challenges for cybersecurity professionals. Renée Burton, Head of Threat Intelligence at Infoblox, emphasizes that DNS-based TDSs are often overlooked, with a prevailing focus on HTTP-based systems.
However, Savvy Seahorse has been operational since at least August 2021, operating in the shadows and evading conventional detection methods.
The key to Savvy Seahorse's success lies in its exploitation of CNAME records. In the DNS realm, CNAME allows multiple domains to map to a single base (canonical) domain. This seemingly innocuous feature is manipulated by Savvy Seahorse to rapidly scale and relocate its operations.
When one phishing site is shut down, the threat actor effortlessly shifts to a new one, relying on CNAME as a map to mirror sites.
CNAME not only applies to domains but extends to IP addresses. In the event of a hosting infrastructure shutdown, Savvy Seahorse can swiftly redirect its CNAME to a different address, ensuring resilience and evading detection.
The attacker's ability to advertise any subdomain for a brief period further complicates tracking and takedown efforts.
Crucially, CNAME serves as both Savvy Seahorse's strength and vulnerability. While the threat actor has cunningly utilized 30 domain registrars and 21 ISPs to host 4,200 domains, they all trace back to a single base domain: b36cname[.]site. This centralized link becomes Savvy Seahorse's Achilles' heel, presenting a unique opportunity for defenders.
From a threat intelligence perspective, countering Savvy Seahorse involves a relatively straightforward approach – blocking the one base domain to which the CNAME points. Renée Burton notes that despite the existence of thousands of malicious domains, there's only one malicious CNAME. This single point of failure provides defenders with a potent strategy, allowing them to neutralize the entire threat with one decisive action.
While attackers theoretically have the option to build malicious networks using multiple CNAMEs, Burton highlights a trend among cybercriminals to aggregate towards a smaller set of CNAMEs. This strategic choice, possibly driven by a desire to avoid detection, simplifies the task for defenders, who can focus efforts on a limited number of CNAMEs associated with the threat.
Savvy Seahorse's exploitation of DNS-based TDS with CNAME records presents a new frontier in cyber threats. The intricate dance between attackers and defenders highlights the importance of understanding and adapting to evolving tactics. As defenders fortify their strategies, the hope is to stay one step ahead of sophisticated threat actors like Savvy Seahorse, ensuring a safer digital landscape for individuals and organizations alike.
