Using system signals

The following information provides you with details about the various system signals:

  • Long name: the name of the signal that you can use to verbally reference or describe it.
  • Short name: the name of the signal that is applied to matched requests and that can be used to search within the Next-Gen WAF web interface.
  • Usable in: outlines where a signal can be used. The options are Lists, Rate Limit Rules, Request Rules, or Signal Exclusions. None indicates that the signal may be provided but cannot be used outside of its informational context.
  • Description: an outline of what the signal means or what it indicates.

Attacks

Attack signals are labels that describe malicious requests that contain attack payloads designed to hack, destroy, disable, steal, gain unauthorized access, and otherwise take harmful actions.

Long nameShort nameUsable inDescription
Attack ToolingUSERAGENT
  • Lists
  • Rate Limit Rules
  • Request Rules
  • Signal Exclusion
  • Attack Tooling is the use of automated software to identify security vulnerabilities or to attempt to exploit a discovered vulnerability
    AWS SSRFAWS-SSRF
  • Templated Rule
  • Server Side Request Forgery (SSRF) is a request which attempts to send requests made by the web application to target internal systems. AWS SSRF attacks use SSRF to obtain Amazon Web Services (AWS) keys and gain access to S3 buckets and their data.
    BackdoorBACKDOOR
  • Lists
  • Rate Limit Rules
  • Request Rules
  • Signal Exclusion
  • A backdoor signal is a request that attempts to determine if a common backdoor file exists on a system. The signal generally matches known backdoor filenames. Traditionally these filenames appear with PHP file extensions like admin.php and r57.php. For many users, when these paths return a 200 or a larger response than expected, it may indicate that their system has been compromised or they are unknowingly hosting a backdoor file.
    Command ExecutionCMDEXE
  • Lists
  • Rate Limit Rules
  • Request Rules
  • Signal Exclusion
  • Command Execution is the attempt to gain control or damage a target system through arbitrary system commands by means of user input
    Cross Site ScriptingXSS
  • Lists
  • Rate Limit Rules
  • Request Rules
  • Signal Exclusion
  • Cross-Site Scripting is the attempt to hijack a user's account or web-browsing session through malicious JavaScript code
    Directory TraversalTRAVERSAL
  • Lists
  • Rate Limit Rules
  • Request Rules
  • Signal Exclusion
  • Directory Traversal is the attempt to navigate privileged folders throughout a system in hopes of obtaining sensitive information
    Log4J JNDILOG4J-JNDI
  • Lists
  • Rate Limit Rules
  • Request Rules
  • Signal Exclusion
  • Log4J JNDI attacks attempt to exploit the Log4Shell vulnerability present in Log4J versions earlier than 2.16.0
    SQL InjectionSQLI
  • Lists
  • Rate Limit Rules
  • Request Rules
  • Signal Exclusion
  • SQL Injection is the attempt to gain access to an application or obtain privileged information by executing arbitrary database queries

    Anomalies

    Anomaly signals are labels that describe abnormal requests. While not inherently malicious, abnormal requests may be indicative of unwanted or abusive traffic. Examples include malformed request data and requests originating from known scanners.

    Long nameShort nameUsable inDescription
    Abnormal PathABNORMALPATH
  • Lists
  • Rate Limit Rules
  • Request Rules
  • Signal Exclusion
  • Abnormal Path indicates the original path differs from the normalized path (e.g., /foo/./bar is normalized to /foo/bar)
    Bad Hop HeadersBHH
  • Lists
  • Rate Limit Rules
  • Request Rules
  • Signal Exclusion
  • Bad Hop Headers indicate an HTTP smuggling attempt through either a malformed Transfer-Encoding (TE) or Content-Length (CL) header, or a well-formed TE and CL header
    Blocked RequestsBLOCKEDNoneRequests blocked by the Next-Gen WAF
    Code Injection PHPCODEINJECTION
  • Lists
  • Rate Limit Rules
  • Request Rules
  • Signal Exclusion
  • Code Injection is the attempt to gain control or damage a target system through arbitrary application code commands by means of user input.
    Compression DetectedCOMPRESSED
  • Lists
  • Rate Limit Rules
  • Request Rules
  • Signal Exclusion
  • The POST request body is compressed and cannot be inspected. For example, if a Content-Encoding: gzip request header is specified and the POST body is not plain text.
    Fastly Unknown BackendFASTLY-UNKNOWN-BACKENDIndicates a request to a backend that does not exist in your edge security service.
    Forceful BrowsingFORCEFULBROWSING
  • Signal Exclusion
  • Forceful Browsing is the failed attempt to access admin pages
    GraphQL API QueryGRAPHQL-API
  • Lists
  • Rate Limit Rules
  • Request Rules
  • Signal Exclusion
  • Indicates a GraphQL API request.
    GraphQL Duplicate VariablesGRAPHQL-DUPLICATE-VARIABLES
  • Lists
  • Rate Limit Rules
  • Request Rules
  • Signal Exclusion
  • Indicates a GraphQL request that contains duplicated variables.
    GraphQL Max DepthGRAPHQL-DEPTH
  • Lists
  • Rate Limit Rules
  • Request Rules
  • Signal Exclusion
  • Indicates a request has reached or exceeded the maximum depth allowed on the server for GraphQL API queries
    GraphQL Missing Required Operation NameGRAPHQL-MISSING-REQUIRED-OPERATION-NAME
  • Lists
  • Rate Limit Rules
  • Request Rules
  • Signal Exclusion
  • Indicates a request has multiple GraphQL operations but does not define which operation to execute.
    GraphQL SyntaxGRAPHQL-SYNTAX
  • Lists
  • Rate Limit Rules
  • Request Rules
  • Signal Exclusion
  • Indicates a request that contains invalid GraphQL syntax. This may be related to a programming error or a malicious request.
    GraphQL Undefined VariableGRAPHQL-UNDEFINED-VARIABLES
  • Lists
  • Rate Limit Rules
  • Request Rules
  • Signal Exclusion
  • Indicates a request made to a GraphQL API containing more variables than expected by a function. This can be used to obfuscate malicious requests.
    HTTP 403 ErrorsHTTP403
  • Signal Exclusion
  • Forbidden. This is commonly seen when the request for a url has been protected by the server's configuration.
    HTTP 404 ErrorsHTTP404
  • Signal Exclusion
  • Not Found. This is commonly seen when the request for a page or asset does not exist or cannot be found by the server.
    HTTP 429 ErrorsHTTP429
  • Signal Exclusion
  • Too Many Requests. This is commonly seen when rate-limiting is used to slow down the number of active connections to a server.
    HTTP 4XX ErrorsHTTP4XX
  • Signal Exclusion
  • 4xx Status Codes commonly refer to client request errors
    HTTP 500 ErrorsHTTP500
  • Signal Exclusion
  • Internal Server Error. This is commonly seen when a request generates an unhandled application error.
    HTTP 503 ErrorsHTTP503
  • Signal Exclusion
  • Service Unavailable. This is commonly seen when a web service is overloaded or sometimes taken down for maintenance.
    HTTP 5XX ErrorsHTTP5XX
  • Signal Exclusion
  • 5xx Status Codes commonly refer to server related issues
    HTTP Response SplittingRESPONSESPLIT
  • Lists
  • Rate Limit Rules
  • Request Rules
  • Signal Exclusion
  • Identifies when CRLF characters are submitted as input to the application to inject headers into the HTTP response
    Invalid EncodingNOTUTF8
  • Lists
  • Rate Limit Rules
  • Request Rules
  • Signal Exclusion
  • Invalid Encoding can cause the server to translate malicious characters from a request into a response, causing either a denial of service or XSS
    Malformed Data in the request bodyMALFORMED-DATA
  • Lists
  • Rate Limit Rules
  • Request Rules
  • Signal Exclusion
  • A POST, PUT or PATCH request body that is malformed according to the Content-Type request header. For example, if a Content-Type: application/x-www-form-urlencoded request header is specified and contains a POST body that is json. This is often a programming error, automated or malicious request.
    Malicious IP TrafficSANS
  • Lists
  • Rate Limit Rules
  • Request Rules
  • Signal Exclusion
  • The regularly imported SANS Internet Storm Center list of IP addresses that have been reported to have engaged in malicious activity
    SigSci Malicious IPsSIGSCI-IP
  • Lists
  • Rate Limit Rules
  • Request Rules
  • Signal Exclusion
  • Whenever an IP is flagged due to a malicious signal by our decision engine, that IP will be propagated to all customers. We then log subsequent requests from those IP addresses that contain any additional signal for the duration of the flag.
    Missing Content-Type request headerNO-CONTENT-TYPE
  • Lists
  • Rate Limit Rules
  • Request Rules
  • Signal Exclusion
  • A POST, PUT or PATCH request that does not have a Content-Type request header. By default application servers should assume Content-Type: text/plain; charset=us-ascii in this case. Many automated and malicious requests may be missing Content Type.
    No User AgentNOUA
  • Lists
  • Rate Limit Rules
  • Request Rules
  • Signal Exclusion
  • Many automated and malicious requests use fake or missing User-Agents to make it difficult to identify the type of device making the requests
    Null ByteNULLBYTE
  • Lists
  • Rate Limit Rules
  • Request Rules
  • Signal Exclusion
  • Null bytes do not normally appear in a request and indicate the request is malformed and potentially malicious
    Out-of-Band DomainOOB-DOMAIN
  • Lists
  • Rate Limit Rules
  • Request Rules
  • Signal Exclusion
  • Out-of-Band domains are generally used during penetration testing to identify vulnerabilities in which network access is allowed.
    Private FilesPRIVATEFILE
  • Lists
  • Rate Limit Rules
  • Request Rules
  • Signal Exclusion
  • Private files are usually confidential in nature, such as an Apache .htaccess file, or a configuration file which could leak sensitive information
    ScannerSCANNER
  • Lists
  • Rate Limit Rules
  • Request Rules
  • Signal Exclusion
  • Identifies popular scanning services and tools
    SearchBot ImpostorIMPOSTOR
  • Templated Rule
  • Search bot impostor is someone pretending to be a Google or Bing search bot, but who is not legitimate
    Site Flagged IPSITE-FLAGGED-IP
  • Lists
  • Rate Limit Rules
  • Request Rules
  • Signal Exclusion
  • Indicates a request was received from an IP that was flagged for exceeding attack thresholds for a specific site. This signal is only included with the Premier platform.

    Bots

    Bot signals are labels that describe suspected and verified bot requests.

    Long nameShort nameUsable inDescription
    AccessibilityVERIFIED-BOT.ACCESSIBILITY
  • Lists
  • Rate Limit Rules
  • Request Rules
  • Signal Exclusion
  • Tools that make content accessible (e.g., screen readers).
    Challenge Token InvalidCHALLENGE-TOKEN-INVALID
  • Lists
  • Rate Limit Rules
  • Request Rules
  • Signal Exclusion
  • Indicates a request that did not include a valid bot challenge token.
    Challenge Token ValidCHALLENGE-TOKEN-VALID
  • Lists
  • Rate Limit Rules
  • Request Rules
  • Signal Exclusion
  • Indicates a request that included a valid bot challenge token.
    Challenged RequestCHALLENGEDNoneIndicates a request that was issued a client challenge by the Next-Gen WAF.
    Content FetcherVERIFIED-BOT.CONTENT-FETCHER
  • Lists
  • Rate Limit Rules
  • Request Rules
  • Signal Exclusion
  • Tools that extract content from websites to be used elsewhere.
    Monitoring & Site ToolsVERIFIED-BOT.MONITORING-SITE-TOOLS
  • Lists
  • Rate Limit Rules
  • Request Rules
  • Signal Exclusion
  • Tools that access your site to monitor things like performance, uptime, and proving domain control.
    Online MarketingVERIFIED-BOT.ONLINE-MARKETING
  • Lists
  • Rate Limit Rules
  • Request Rules
  • Signal Exclusion
  • Crawlers from online marketing platforms (e.g., Facebook, Pinterest).
    Page PreviewVERIFIED-BOT.PAGE-PREVIEW
  • Lists
  • Rate Limit Rules
  • Request Rules
  • Signal Exclusion
  • Tools that access your site to show a preview of the page, in other online services, and social media platforms.
    Platform IntegrationsVERIFIED-BOT.PLATFORM-INTEGRATIONS
  • Lists
  • Rate Limit Rules
  • Request Rules
  • Signal Exclusion
  • Integration with other platforms by accessing the website's API, notably Webhooks.
    ResearchVERIFIED-BOT.RESEARCH
  • Lists
  • Rate Limit Rules
  • Request Rules
  • Signal Exclusion
  • Commercial and academic tools that collect and analyze data for research purposes.
    Search Engine CrawlerVERIFIED-BOT.SEARCH-ENGINE-CRAWLER
  • Lists
  • Rate Limit Rules
  • Request Rules
  • Signal Exclusion
  • Crawlers that index your site for search engines.
    Search Engine OptimizationVERIFIED-BOT.SEARCH-ENGINE-OPTIMIZATION
  • Lists
  • Rate Limit Rules
  • Request Rules
  • Signal Exclusion
  • Tools that support search engine optimization tasks (e.g., link analysis, ranking).
    Security ToolsVERIFIED-BOT.SECURITY-TOOLS
  • Lists
  • Rate Limit Rules
  • Request Rules
  • Signal Exclusion
  • Security analysis tools that inspect your site for vulnerabilities, misconfigurations and other security features.
    Suspected Bad BotSUSPECTED-BAD-BOT
  • Lists
  • Rate Limit Rules
  • Request Rules
  • Signal Exclusion
  • Indicates a request that is suspected of being a bad bot.
    Suspected BotSUSPECTED-BOT
  • Rate Limit Rules
  • Request Rules
  • Signal Exclusion
  • Indicates a request that is suspected of being a bot.

    Informational

    Informational signals are labels that describe common request properties that aren't malicious or abnormal.

    Long nameShort nameUsable inDescription
    Allowed RequestsALLOWED
  • Lists
  • Rate Limit Rules
  • Request Rules
  • Signal Exclusion
  • Indicates a request that is allowed due to a rule with an allow action. Requests with this signal are never blocked.
    Datacenter TrafficDATACENTER
  • Lists
  • Rate Limit Rules
  • Request Rules
  • Signal Exclusion
  • Datacenter Traffic is non-organic traffic originating from identified hosting providers. This type of traffic is not commonly associated with a real end user.
    Double EncodingDOUBLEENCODING
  • Lists
  • Rate Limit Rules
  • Request Rules
  • Signal Exclusion
  • Double Encoding checks for the evasion technique of double encoding html characters
    Fail OpenFAIL-OPEN
  • Lists
  • Rate Limit Rules
  • Request Rules
  • Signal Exclusion
  • Indicates a request was allowed because the WAF failed open
    GraphQL IDEGRAPHQL-IDE
  • Rate Limit Rules
  • Request Rules
  • Indicates a request originating from a GraphQL Interactive Development Environment (IDE).
    GraphQL IntrospectionGRAPHQL-INTROSPECTION
  • Lists
  • Rate Limit Rules
  • Request Rules
  • Signal Exclusion
  • Indicates an attempt to obtain the schema of a GraphQL API. The schema can be used to identify which resources are available, informing subsequent attacks.
    JSON Encoding ErrorJSON-ERROR
  • Signal Exclusion
  • A POST, PUT, or PATCH request body that is specified as containing JSON within the Content-Type request header but contains JSON parsing errors. This is often related to a programming error or an automated or malicious request.
    Tor TrafficTORNODE
  • Lists
  • Rate Limit Rules
  • Request Rules
  • Signal Exclusion
  • Tor is software that conceals a user's identity. A spike in Tor traffic can indicate an attacker trying to mask their location.
    Weak TLSWEAKTLS
  • Signal Exclusion
  • Weak TLS. A web server's configuration allows SSL/TLS connections to be established with an obsolete cipher suite or protocol version. This signal is based on inspecting a small percent of requests. Also, some architectures and Signal Sciences' language SDK modules do not support this signal.
    XML Encoding ErrorXML-ERROR
  • Signal Exclusion
  • A POST, PUT, or PATCH request body that is specified as containing XML within the Content-Type request header but contains XML parsing errors. This is often related to a programming error or an automated or malicious request.
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