CorrelationCorrelation identifies potential security threats by identifying relationships between multiple types of events occurring in two or more assets. is the processing of the eventAny traffic or data exchange detected by AT&T Cybersecurity products through a sensor, or through external devices such as a firewall. stream in order to identify important events or patterns of events within large volumes of data. The logic to identify these events is encapsulated in a Correlation RuleA correlation rule correlates incoming events based on previously defined relationships defined in the correlation directive, associating multiple events, of the same or different event types, from the same data source.. The AT&T Alien Labs™ Security Research Team creates correlation rules, which associate multiple events from one or more data sources to identify potential security threats. These rules identify patterns associated with malicious activityActivity in a system that exceeds or misuses that access in a manner that negatively affects the confidentiality, integrity, or availability of the organization's information systems.. AlarmsAlarms provide notification of an event or sequence of events that require attention or investigation. are generated by an explicit call within these rules.
These rules are created by the Security Research Team and you are not able to modify correlation rules. However, you can use orchestration rules to modify the way USM Anywhere treats events. See Orchestration Rules for more information.
Important: The "Suspicious Behavior - OTX Indicators of Compromise" correlation rule generates alarms if the pulse comes from the AlienVault OTX account.
What Is Correlation?
Correlation is a process performed by the correlation engine on USM Anywhere. It identifies potential security threats by detecting behavior patterns across different types of assetsAn IP-addressable host, including but not limited to network devices, virtual servers, and physical servers., which produce disparate yet related events. Correlation links different events, turning data into more useful information.
The logs received and processed by USM Anywhere carry important information such as what your users are doing, what data is being accessed, how your system and network are performing, and if there are any security threats or attacks taking place. However, reading logs has these disadvantages:
- Logs vary from system to system or even from version to version on the same system.
- Logs have limited perspective, because each system sees events from its own perspective.
- Logs are static, fixed points in time, without the full context or sequence of related events.
The correlation process provides answers to these challenges, putting the events into full context. For example, a network firewallVirtual or physical device designed to defend against unauthorized access to data, resources, or a private network. A firewall’s primary purpose is to create segregation between two or more network resources, blocking undesirable traffic between them. sees packets and network sessions, while an applicationA software program that performs some collection of tasks on a computer or some other programmable device. sees users, data, and requests. While different systems report logs of similar activities, the way in which they articulate these activities is quite different. With the help of correlation rules, USM Anywhere can correlate the two types of events, generating an alarm if a threat exists.
Event correlation enables the security analysts and the incident responders to:
- Make informed decisions on how to respond to security threats.
- Validate effectiveness of existing security controls.
- Measure and report compliance.
- Detect policy violations.
Correlation Rules Structure
The structure of correlation rules is this:
Intent — Strategy — Method
The categorization uses a three-tiered model for describing an observed behavior. The first tier is the ‘Intent’ of the behavior; this roughly maps to the "Intrusion Kill Chain" to provide an understanding of the context of the behavior. The second tier is the strategy the attackerOne who maliciously attempts to bypass security restrictions or negatively impact a system or resource. took, used to describe the methodology employed. The third tier is the "method" of the behavior, used to describe the details of the particular methodology.
The intent describes the context of the behavior that is being observed. These intents roughly map to the stages of the "Intrusion Kill Chains" but collapsed so as to ensure that each is discrete.
From highest to lowest, these are the threat categories:
|System CompromiseState or indication that an intruder has bypassed security measures and gained unauthorized access to resources, installed malicious software, or modified existing software or configurations in an attempt to cause damage or steal information.||Behavior indicating a compromised system.|
|Exploitation & Installation||Behavior indicating a successful exploitPiece of software, data, or a sequence of commands that takes advantage of a flaw or vulnerability to cause unintended or unanticipated behavior to occur in software or hardware, that result in gaining increased privileges and access privileged data. of a vulnerabilityA known issue or weakness in a system, procedure, internal control, software package, or hardware that could be used to compromise security. or backdoor or remote access Trojan being installed on the system.|
|Delivery & Attack||Behavior indicating an attempted delivery of an exploit. This can include detection of malicious email attachments, network-based detection of known attack payloads or analysis-based detection of known attack strategies such as SQL Injection.|
|Reconnaissance & Probing||
Behavior indicating an actor attempting to discover information about your organization. This is broad-based, including everything from port scansProcess in which a series of messages are sent to a computer to probe for open ports. to social engineeringUsing people's inherent goodwill against them in order to violate security. to open-source intelligence.
|Environmental Awareness||Behavior and status about the environment being monitored. This includes information about services running, behavior of users in the environment, and the configuration of the systems.|
The strategy describes the broad-based strategy or behavior that is detected. It is a description of the strategy the malicious user is using to achieve their goal or not. For example, when trying to exploit a known vulnerability in a web browser the attacker is launching a "Client-Side Attack - Known Vulnerability."
The method describes the particular method that the actor employs. To further the previous example, the method would provide additional detail on the target of the attack and the particular vulnerability "Firefox - CVE-2008-4064".
USM Anywhere Correlation Rules
USM Anywhere provides built-in rules and adds more every week through the Alien Labs Threat Intelligence SubscriptionThe AT&T Alien Labs™ Threat Intelligence Subscription provides subscribers with the ability to detect the latest threats with continually updated correlation rules, IDS signatures, vulnerability audits, asset discovery signatures, IP reputation data, collection and data source plugins, and report templates.. Some of these rules are generic, which means that the rule can match data from different data sources. For example, the following rule matches data from different application firewalls:
Some rules are more specific, which means that the rule only matches a particular data source. For example, the following rule only matches data from Watchguard XTM:
Note: When a more specific rule exists in USM Anywhere, it takes precedence over the generic rule.
To see correlation rules
- Go to Settings > Rules.
- In the left navigation panel, click Correlation Rules.
- There is a square box above the table, which you can use for searching a rule and then click the icon.
- Click the rule to expand the details of the rule. You can see the strategy, the method and the rule itself.