What is Cobalt Strike: Why do Attackers Use It?

To evaluate the safety of computer networks and infrastructure, experts created the Cobalt Strike penetration testing tool.

Cobalt Strike aids in simulating attacks, identifying security flaws, and practicing defenses against potential threats like attacks, implant installation, and backdoors. It can create beacon loaders and payloads to detect network vulnerabilities and establish communication with attackers online. The Cobalt Strike payload can provide system details to the attacker and execute their instructions.

Cobalt Strike: What Is It?

Commercially available as Cobalt Strike, it provides security testers with access to a wide range of attack methods. It mimics a wide range of malware and advanced threat techniques, enabling its use for spear phishing and other unauthorized system access methods.

White Cobalt Strike, a legitimate tool costing $3,500 per user, is utilized by both ethical hackers and threat actors. It is popular in the cyber security realm, with some attackers bypassing its software protection by exploiting the trial version.

How Does Cobalt Strike Work?

As a threat emulation program, Cobalt Strike is able to do the following.

Reconnaissance involves identifying client-side programs and their versions in order to pinpoint security vulnerabilities. Additionally, attack packages consist of a social engineering attack engine and Trojans camouflaged as harmless files. Moreover, they include a cloned website for drive-by downloads. Furthermore, the Cobalt Team Server connects group hosts, facilitating collaborative data exchange, real-time conversations, and distributed responsibility for managing compromised machines.

Moreover, Beacon is a dropper used by Cobalt Strike after an exploit has been successfully exploited. It can not only download files but also take screenshots, execute payloads, and log keystrokes.

By utilizing covert channels of communication, hackers can instantly alter the visibility indicators of their network. They can egress into a network via HTTP, HTTPS, DNS, or SMB, and then load a C2 profile to disguise their true identity.

Additionally, two-factor authentication can be bypassed using browser pivoting.

How and Why Do Attackers Use Cobalt Strike?

Hackers utilize Cobalt Strike, malware, to gain unauthorized access to computer systems covertly.

Malicious software (or “malware,” as defined by Google) is software with the express intention of causing damage to a computer. When you download malicious software onto your computer, it can steal sensitive information, slow down your system, and even send spam from your email account.

Viruses, Trojans, worms, and spyware like TrickBot, Hancitor, Emotet, and Adwind are all fair game.

Cobalt Strike is a pervasive cyber threat that can be installed on a victim’s computer without much effort. Infected websites, phishing emails, and USB drives are all potential entry points for this malware.

Hackers and threat actors prefer it due to its obfuscation capabilities, user-friendliness, and dual-functionality as a downloader (in either the first or second stage). In order to break into a business’s network, they frequently employ the use of Cobalt Strike. This gives them the opportunity to steal sensitive data or cause system failures for the business.

Cobalt Strike can do a lot more than just steal passwords; it can also take screenshots, record keystrokes, and add the victim’s computer to a botnet. Cybercriminals and APT actors are utilizing it to commit fraud and steal money from bank accounts.

Among its many features, Cobalt Strike’s most valuable capability for threat actors is establishing connections through its servers. This allows them to compromise networks and establish persistent channels with the target.

Beacon, a payload (or agent) provided by Cobalt Strike, can be installed as a client for the attackers on the targeted machine as a post-exploitation tool, allowing them to perform additional actions after a successful exploit. Once activated, the Beacon enables covert file uploads and command and control instructions—exactly what sophisticated threat actors seek.

Cobalt Strike’s Command and Control protocol differs from traditional HTTP traffic by utilizing the Domain Name System (DNS), making it harder to detect. The Beacon decodes DNS entries and an obfuscation algorithm to conceal malicious instructions cleverly.

After installing the Beacon, various harmful actions can occur, including network monitoring, data exfiltration, further lateral movement, and the deployment of ransomware.

Cobalt Strike Detection

Detecting Cobalt Strike servers can be challenging, but unpatched versions of the software are more obvious. It is possible to detect a Cobalt Strike deployment using a combination of the following methods:

• Try locating the official developer’s default TLS certificate. If the admin didn’t change this, then it’s definitely a sign.
• If the DNS server is too busy to respond to a query, it will instead reply with a fake IP address (0.0.0.0).
• Do a port scan on 50050/TCP.
• Check for a 404 Not Found error with an HTTP request.
• There may still be room for error, but combining various detection methods should provide results with a high degree of confidence. However, the simplest way to identify a host running Cobalt Strike remains to use the pre-installed TLS certificate.
• Trace the path of the suspicious network traffic and check for TLS negotiation between the host and the remote server. A  server’s identification relies on its TLS fingerprint, containing details such as protocol version, approved ciphers, and elliptic curve data. For generating SSL client fingerprints, JA3 is a useful tool.

Conclusion

Ethical hackers and malicious actors utilize Cobalt Strike to penetrate systems, identify vulnerabilities, and simulate attacks. Its features enable actions like data exfiltration, network monitoring, and ransomware deployment. Cobalt Strike’s obfuscation techniques and covert communication make detection challenging, but analyzing TLS certificates and network traffic can provide insights. Organizations must remain vigilant, implement robust security measures, and update defenses to mitigate risks from ongoing unauthorized access attempts.