ThreatPattern Definitions » History » Version 2
« Previous -
Version 2/15
(diff) -
Next » -
Current version
Luke Murphey, 04/03/2010 01:35 AM
ThreatPattern Definitions¶
ThreatPattern's similar in concept to the signatures used by the Snort IDS system. Below is a sample rule:
Alert("Abuse.DataHiding.Rar_File_In_Jpeg"){
Message="A JPEG file with a RAR file appended was observed";
Severity="Low";
ID=1000194;
Version=1;
BasicEncoding;
Byte="FF D9";
String="Rar!"; Offset=0;
ContentType="image/jpeg";
Reference=url,lifehacker.com/software/encryption/hide-files-in-jpeg-images-207905.php;
Reference=url,schmidt.devlib.org/file-formats/rar-archive-file-format.html;
}
Definition Verb¶
The rules start with a action that indicates what the system should do with the rule. The action verbs are as follows:
| Verb | Operation | Notes |
| Eval | Causes the rule to be evaluated but no action taken. | Only valid when an Set option is used. Used to set a flag that may be used in another signature (allows the rules to maintain state). |
| Alert | Causes the rule to indicate that a match has been found. | Used only to determine if the site may be compromised. |
| Block | Causes the resource to be blocked (end user cannot access) | Useful when using a proxy to control access to the servers; this is not currently used yet. |
Definitions must have a name that is composed of three parts: a category, sub-category, and name. The part are separated by periods (like "category.subcategory.name"). The category and sub-category are important because the user can create exceptions and disable definitions by category or sub-category. Therefore, it is important that you use category names that makes sense; otherwise, the user may disable or enable your definition inadvertently.
In some cases a definition may be created for a specific site-group or rule. It is recommended that the definition be named such it is clear it is site-group or rule specific. Oftentimes, this done by appending an underscore to the category name (e.g. "_Acme.InformationLeak.ConfidentialDocumentFound").
Definition Body¶
The definition is composed of options that are used to make conclusions about the data provided. Below is a list of the various options:
| Option | Required | Value | Example | Description |
| ID | Yes | <integer> | ID=10012441 | |
| Message | Yes | <string> | Message="Malicious Website Discovered" | |
| Version | <integer> | Version=3 | ||
| String | <string> | String=haxored | Looks for the given String value | |
| Regex | PCRE | Regex=/apple/i | Looks for the given Regex (in PCRE format) | |
| Byte | Bytes | Byte=90 90 90 | Looks for the given bytes | |
| Set | <string> | Set="IframeFound" | Sets the given variable (allows rules to maintain state) | |
| UnSet | <string> | UnSet="IframeFound" | Unsets the given variable (allows rules to maintain state) | |
| IfSet | <string> | IfSet="ActiveX" | Makes the action dependent upon whether the variable exists | |
| IfNotSet | <string> | IfNotSet="ActiveX" | Opposite of above | |
| Toggle | <string> | Toggle="JavaScriptFound" | ||
| Offset | <integer> | Offset=128 | Sets how much data should be skipped from the previous operator | |
| Depth | <integer> | Depth=1024 | Sets a maximum depth into the data that the definition will examine (relative to the beginning of the data stream) | |
| Within | <integer> | Within=512 | Sets how many characters or bytes to analyze for the previous option before giving up. This is oftentimes used to increase the performance of definitions by limiting the amount of data they have to analyze. | |
| ByteTest | operation | 4 digits >= 128 (hexadecimal) | Can accept options such as big-endian, little-endian, hexadecimal, absolute-value and can operate on both digits (character representations of a number) or bytes (integer values) | |
| ByteJump | operation | 4 bytes (big-endian, align-8) | Can accept options such as big-endian, little-endian, hexadecimal, absolute-value, octal, align-4 and align-8 and can operate on both digits (character representations of a number) or bytes (integer values) | |
| Reference | <string> | url,threatfactor.com | Types of references are: url ,bugtraq, cve, nessus, arachnids, mcafee | |
| BasicEncoding | <string> | Causes the evaluator to skip character set encoding and treat the data as if it is raw bytes (or ASCII encoded) | ||
| IsDataAt | <integer> | Determines if data is at the given position (i.e. equates to false if the data stream ends before the value provided) | ||
| Severity | <string> | Severity="Medium" | Must be either low, medium or high and is required if the definition verb is alert or block | |
| ContentType | PCRE or <string> | ContentType=/text.*//i | Matches a given content type. The content type is inferred by the scanning engine based upon the file contents, HTTP headers and file extension. | |
| URI | <string> | URI="http://google.com" | ||
| IgnoreCase | Synonymous with "NoCase" |