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.

What Is Cobalt Strike?

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 It Work?

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

Reconnaissance

“Cobalt Strike starts by looking closely at the programs on a computer and figuring out their exact versions. This careful check helps the program find potential weak points in security. It also comes with a tool for tricky social engineering attacks and Trojans that pretend to be harmless files. The attack kit even includes a copied website made for sneaky drive-by downloads, making it better at taking advantage of the target computer systems.”

Cobalt Team Server

The Cobalt Team Server plays a pivotal role in Cobalt Strike’s operation. It connects group hosts, fostering collaborative data exchange, real-time conversations, and distributed responsibility for managing compromised machines. This centralized control mechanism provides hackers with the means to coordinate and manipulate compromised systems efficiently.

Beacon

Following a successful exploit, Cobalt Strike deploys Beacon as a dropper. Beacon is a versatile tool capable of multifaceted actions. It can download files, capture screenshots, execute payloads, and log keystrokes. This post-exploitation capability enhances the depth of control that Cobalt Strike exerts over a compromised system.

Covert Communication

To maintain stealth, Cobalt Strike employs covert channels of communication. This strategic approach enables hackers to instantly alter the visibility indicators of their network. They achieve this by egressing into a network through various protocols such as HTTP, HTTPS, DNS, or SMB. Subsequently, a C2 profile is loaded, effectively concealing the true identity of the malicious activity.
Load a C2 profile to disguise their true identity.

Two-Factor Authentication Bypass

Cobalt Strike employs a technique known as browser pivoting to bypass two-factor authentication. This method allows hackers to manipulate the authentication process through the victim’s browser, showcasing the program’s adaptability and ingenuity in overcoming security measures.

How and Why Do Attackers Use Cobalt Strike?

Hackers often use Cobalt Strike, a form of malware, to secretly enter computer systems without permission. Malicious software, known as “malware,” is intentionally designed to harm computers. When you download this kind of software, it can steal important information, slow down your computer, and even send unwanted emails.

Types of Malware

Various types of malware, such as viruses, Trojans, worms, and spyware (e.g., TrickBot, Hancitor, Emotet, Adwind), are commonly used by hackers for harmful activities.

Entry Points for Cobalt Strike

Cobalt Strike poses a widespread cyber threat, easily getting onto a victim’s computer through infected websites, phishing emails, or USB drives.

Why Hackers Prefer Cobalt Strike

Hackers favor Cobalt Strike due to its ability to hide (obfuscation), user-friendly features, and its dual-purpose as a downloader. It is frequently used to breach business networks, allowing hackers to steal sensitive data or disrupt a company’s systems.

Capabilities of Cobalt Strike

Beyond password theft, Cobalt Strike can take screenshots, record keystrokes, and add a victim’s computer to a botnet. Cybercriminals and APT (Advanced Persistent Threat) actors use it for fraud and stealing money from bank accounts.

Valuable Features

One of Cobalt Strike’s crucial features is establishing connections through its servers. This enables hackers to compromise networks and create persistent channels with their target.

Beacon Payload

Beacon, a tool provided by Cobalt Strike, serves as a payload or agent. Installed as a client on the targeted machine, it acts as a post-exploitation tool for additional actions after a successful exploit. Activated Beacons enable covert file uploads and command and control instructions—perfect for sophisticated threat actors.

Command and Control Protocol

Cobalt Strike’s Command and Control protocol sets it apart from regular HTTP traffic by using the Domain Name System (DNS), making detection more challenging. The Beacon cleverly decodes DNS entries and an obfuscation algorithm to hide malicious instructions.

After Beacon Installation

Once Beacon is installed, hackers can carry out harmful actions, including network monitoring, data exfiltration, lateral movement through the network, 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

“Good hackers and bad ones use Cobalt Strike to get into computer systems, find weak points, and practice attacks. It can do things like taking out data, watching networks, and even putting ransomware in. Cobalt Strike is tricky to find because it hides and talks secretly, but looking at special certificates and how the network works can help. To stay safe, companies need to watch out, use strong security, and keep their defenses up to stop unauthorized access.”