Browse Definitions :
Definition

command-and-control server (C&C server)

Contributor(s): Matthew Haughn

A command and control server (C&C server) is a computer that issues directives to digital devices that have been infected with rootkits or other types of malware, such as ransomware. C&C servers can be used to create powerful networks of infected devices capable of carrying out distributed denial-of-service (DDoS) attacks, stealing data, deleting data or encrypting data in order to carry out an extortion scheme. In the past, a C&C server was often under an attacker's physical control and could remain active for several years. Today, C&C servers generally have a short shelf life; they often reside in legitimate cloud services and use automated domain generation algorithms (DGAs) to make it more difficult for law enforcement and white hat malware hunters to locate them. 

A malicious network under a C&C server's control is called a botnet and the network nodes that belong to the botnet are sometimes referred to as zombies. In a traditional botnet, the bots are infected with a Trojan horse and use Internet Relay Chat (IRC) to communicate with a central C&C server. These botnets were often used to distribute spam or malware and gather misappropriated information, such as credit card numbers. 

Popular botnet topologies include:

  • Star topology - the bots are organized around a central server.
  • Multi-server topology - there are multiple C&C servers for redundancy.
  • Hierarchical topology - multiple C&C servers are organized into tiered groups.
  • Random topology - coopted computers communicate as a peer-to-peer botnet (P2P botnet).

Since IRC communication was typically used to command botnets, it is often guarded against. This has motivated the drive for more covert ways for C&C servers to issue commands. Alternative channels used for botnet command include JPG images, Microsoft Word files and posts from LinkedIn or Twitter dummy accounts.

Learn more about botnet command and control in this video:

This was last updated in January 2017

Continue Reading About command-and-control server (C&C server)

SearchCompliance

SearchSecurity

  • cyber attack

    A cyber attack is any attempt to gain unauthorized access to a computer, computing system or computer network with the intent to ...

  • backdoor (computing)

    A backdoor is a means to access a computer system or encrypted data that bypasses the system's customary security mechanisms.

  • post-quantum cryptography

    Post-quantum cryptography, also called quantum encryption, is the development of cryptographic systems for classical computers ...

SearchHealthIT

SearchDisasterRecovery

  • risk mitigation

    Risk mitigation is a strategy to prepare for and lessen the effects of threats faced by a business.

  • call tree

    A call tree is a layered hierarchical communication model that is used to notify specific individuals of an event and coordinate ...

  • Disaster Recovery as a Service (DRaaS)

    Disaster recovery as a service (DRaaS) is the replication and hosting of physical or virtual servers by a third party to provide ...

SearchStorage

  • cloud SLA (cloud service-level agreement)

    A cloud SLA (cloud service-level agreement) is an agreement between a cloud service provider and a customer that ensures a ...

  • NOR flash memory

    NOR flash memory is one of two types of non-volatile storage technologies.

  • RAM (Random Access Memory)

    RAM (Random Access Memory) is the hardware in a computing device where the operating system (OS), application programs and data ...

Close