RSS for Slack

Detect Malicious Port Sweep Activities

We are excited to announce support for a new detection type – the identification of malicious port sweeps.

Port sweeps can occur when compromised hosts or containers within your environment probe a port on a large number of publicly routable IP addresses or a large number of internal IP addresses. This type of activity is typically used to find vulnerable hosts or services to exploit.

Port sweeps are conceptually related to port scans, with port sweeps looking for a specific port or ports across multiple hosts, and port scans enumerating any ports to be found on one or more hosts. Sometimes attackers will use a port sweep to narrow down their attack surface, and follow with a port scan, targeted at finding a vulnerable service.

TCP Ports

TCP ports number from 0 to 65535, with the standard ports occupying numbers 0 to 1023. Discovering that a standard port is “open” can indicate either an already infected port, or one that is vulnerable to attack. 

Commonly used ports include:

  • Port 20 (UDP): File Transfer Protocol (FTP) for data transfer
  • Port 22 (TCP): Secure Shell (SSH) protocol for secure logins, FTP, and port forwarding
  • Port 23 (TCP): Telnet protocol for unencrypted text commutations
  • Port 53 (UDP): Domain Name System (DNS) translates names of all computers on internet-to-IP addresses
  • Port 80 (TCP): World Wide Web HTTP

Indicators of Compromise

Potentially malicious port sweeps are detected through their suspicious access patterns – including repeated attempts to connect to a port with a large number of publicly routable IP addresses over a short period of time, or using a large number of internal IP addresses to connect to a port or ports over a short period of time. A port sweep attack aims to locate open ports to discover which services the machine is running and to identify its operating system, to inform which vulnerabilities to exploit.

Internally-based port sweeps are similar to port scan attacks, but rather than leveraging an external application to scan for vulnerable hosts through repeated port scans, internal port sweeps use compromised internal resources to perform port sweeps, with the same goal of identifying vulnerable hosts.

A port sweep can provide useful information about a network environment, including: 

  • Existing network defenses, such as firewalls
  • Running applications
  • Machines that are online
  • Information about the targeted system
  • Information about vulnerable networks and servers

Attackers can then use this information to conduct an attack on a virtual machine or container.

Upwind leverages runtime data and machine learning to rapidly identify unusual port sweeps and immediately alert you to suspicious activity. Read more about port sweep detections in the Upwind Documentation Center (login required).

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Detect Unusual DoT Communications

We are excited to announce a new detection type, identifying unusual DoT activity.

This detection notifies you of unusual DNS over TLS (Transport Layer Security) communication, often referred to as DoT, which could indicate attempts to blend malicious communications with regular encrypted web traffic to evade detection.

DNS over TLS (DoT) 

DNS is a crucial part of infrastructure that maps out IP addresses for hosts connected to the internet through a process called DNS resolution, allowing users to access websites with user-friendly names rather than remembering specific IP addresses for sites.

DNS is a fundamentally “insecure” network whose communication can easily be intercepted. To avoid security risks, DNS needs TLS or HTTPS (Hypertext Transfer Protocol Secure) encryption protocols to improve network security.

TLS is a widely-used protocol that is designed to keep data secure in Internet communications. By using DNS over TLS, users can protect data that is being transferred, keeping it private even if it is intercepted. By using DNS over TLS (DoT), you send DNS requests over an encrypted TLS tunnel and can ensure the data is not readable by unauthorized parties – acting as a needed safeguard against data breaches. 

This is why DoT has become a popular method of safeguarding DNS communications.

Indicators of Compromise 

While DoT helps safeguard data, it can still be compromised by attackers. Upwind detects when a host or container in your cloud environment engages in DoT communication that deviates from established baseline behavior, which may indicate a “Command and Control” or “Defense Evasion” attempt using encrypted channels. This unusual communication could indicate an attacker’s method to compromise your system remotely, exfiltrate data, or deliver further payloads, blending malicious communications with regular encrypted web traffic to evade detection.

Upwind leverages runtime data to rapidly identify unusual DNS over TLS (DoT) communication and immediately alert you to suspicious activity. Read more about DNS over TLS (DoT) detections in the Upwind Documentation Center.

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