SIEM anomaly detection configurations

Identifies OS processes that do not usually use the network but have unexpected network activity, which can indicate command-and-control, lateral movement, persistence, or data exfiltration activity.

A process with unusual network activity can denote process exploitation or injection, where the process is used to run persistence mechanisms that allow a malicious actor remote access or control of the host, data exfiltration, and execution of unauthorized network applications.

Identifies unusual destination port activity that can indicate command-and-control, persistence mechanism, or data exfiltration activity.

Rarely used destination port activity is generally unusual in Linux fleets, and can indicate unauthorized access or threat actor activity.

Searches for unusual listening ports that can indicate execution of unauthorized services, backdoors, or persistence mechanisms.

Searches for unusual web URL requests from hosts, which can indicate malware delivery and execution.

Wget and cURL are commonly used by Linux programs to download code and data. Most of the time, their usage is entirely normal. Generally, because they use a list of URLs, they repeatedly download from the same locations. However, Wget and cURL are sometimes used to deliver Linux exploit payloads, and threat actors use these tools to download additional software and code. For these reasons, unusual URLs can indicate unauthorized downloads or threat activity.

Searches for rare processes running on multiple hosts in an entire fleet or network.

This reduces the detection of false positives since automated maintenance processes usually only run occasionally on a single machine but are common to all or many hosts in a fleet.

Searches for activity from users who are not normally active, which can indicate unauthorized changes, activity by unauthorized users, lateral movement, and compromised credentials.

In organizations, new usernames are not often created apart from specific types of system activities, such as creating new accounts for new employees. These user accounts quickly become active and routine.

Events from rarely used usernames can point to suspicious activity. Additionally, automated Linux fleets tend to see activity from rarely used usernames only when personnel log in to make authorized or unauthorized changes, or threat actors have acquired credentials and log in for malicious purposes. Unusual usernames can also indicate pivoting, where compromised credentials are used to try and move laterally from one host to another.

Searches for unusually large numbers of DNS queries for a single top-level DNS domain, which is often used for DNS tunneling.

DNS tunneling can be used for command-and-control, persistence, or data exfiltration activity. For example, dnscat tends to generate many DNS questions for a top-level domain as it uses the DNS protocol to tunnel data.

Searches for rare and unusual DNS queries that indicate network activity with unusual domains is about to occur. This can be due to initial access, persistence, command-and-control, or exfiltration activity.

For example, when a user clicks on a link in a phishing email or opens a malicious document, a request may be sent to download and run a payload from an uncommon domain. When malware is already running, it may send requests to an uncommon DNS domain the malware uses for command-and-control communication.

Searches for rare and unusual DNS queries that indicate network activity with unusual domains is about to occur. This can be due to initial access, persistence, command-and-control, or exfiltration activity.

For example, when a user clicks on a link in a phishing email or opens a malicious document, a request may be sent to download and run a payload from an uncommon HTTP or TLS server. When malware is already running, it may send requests to an uncommon DNS domain the malware uses for command-and-control communication.

Searches for rare and unusual URLs that indicate unusual web browsing activity. This can be due to initial access, persistence, command-and-control, or exfiltration activity.

For example, in a strategic web compromise or watering hole attack, when a trusted website is compromised to target a particular sector or organization, targeted users may receive emails with uncommon URLs for trusted websites. These URLs can be used to download and run a payload. When malware is already running, it may send requests to uncommon URLs on trusted websites the malware uses for command-and-control communication. When rare URLs are observed being requested for a local web server by a remote source, these can be due to web scanning, enumeration or attack traffic, or they can be due to bots and web scrapers which are part of common Internet background traffic.

Searches for rare and unusual user agents that indicate web browsing activity by an unusual process other than a web browser. This can be due to persistence, command-and-control, or exfiltration activity. Uncommon user agents coming from remote sources to local destinations are often the result of scanners, bots, and web scrapers, which are part of common internet background traffic.

Much of this is noise, but more targeted attacks on websites using tools like Burp or SQLmap can sometimes be discovered by spotting uncommon user agents. Uncommon user agents in traffic from local sources to remote destinations can be any number of things, including harmless programs like weather monitoring or stock-trading programs. However, uncommon user agents from local sources can also be due to malware or scanning activity.

Identifies rare processes that do not usually run on individual hosts, which can indicate execution of unauthorized services, malware, or persistence mechanisms.

Processes are considered rare when they only run occasionally as compared with other processes running on the host.

Identifies an unusually high number of authentication attempts.

Identifies processes started from atypical folders in the file system, which might indicate malware execution or persistence mechanisms.

In corporate Windows environments, software installation is centrally managed and it is unusual for programs to be executed from user or temporary directories. Processes executed from these locations can denote that a user downloaded software directly from the internet or a malicious script/macro executed malware.

Identifies unusual parent-child process relationships that can indicate malware execution or persistence mechanisms.

Malicious scripts often call on other applications and processes as part of their exploit payload. For example, when a malicious Office document runs scripts as part of an exploit payload, Excel or Word may start a script interpreter process, which, in turn, runs a script that downloads and executes malware. Another common scenario is Outlook running an unusual process when malware is downloaded in an email.

Monitoring and identifying anomalous process relationships is an excellent way of detecting new and emerging malware that is not yet recognized by anti-virus scanners.

Searches for PowerShell scripts with unusual data characteristics, such as obfuscation, that may be a characteristic of malicious PowerShell script text blocks.

Searches for unusual Windows services that can indicate execution of unauthorized services, malware, or persistence mechanisms.

In corporate Windows environments, hosts do not generally run many rare or unique services. This job helps detect malware and persistence mechanisms that have been installed and run as a service.

Searches for unusual user context switches using the runas command or similar techniques, which can indicate account takeover or privilege escalation using compromised accounts. Privilege elevation using tools like runas is more common for domain and network administrators than professionals who are not members of the technology department.

Searches for unusual remote desktop protocol (RDP) logins, which can indicate account takeover or credentialed persistence using compromised accounts. RDP attacks, such as BlueKeep, also tend to use unusual usernames.