{"description":"Trending threats, MITRE ATT\u0026CK coverage, and detection metadata. Fed continuously.","feed_url":"https://feed.craftedsignal.io/tags/fuzzing/feed.json","home_page_url":"https://feed.craftedsignal.io/","items":[{"_cs_actors":[],"_cs_cpes":[],"_cs_cves":[],"_cs_exploited":false,"_cs_has_poc":false,"_cs_poc_references":[],"_cs_products":["Nginx","Apache HTTP Server","Apache Tomcat","IIS","Traefik"],"_cs_severities":["low"],"_cs_tags":["web-server","reconnaissance","vulnerability-scanning","fuzzing"],"_cs_type":"advisory","_cs_vendors":["Nginx","Apache","Microsoft","Traefik"],"content_html":"\u003cp\u003eThis threat brief addresses the risk of reconnaissance activities targeting web servers, specifically focusing on the detection of unusual spikes in HTTP error response codes (500, 502, 503, and 504). An adversary might employ vulnerability scanning or fuzzing techniques to identify weaknesses in web applications. These actions often result in a high volume of error responses as the attacker probes various endpoints and inputs. The detection rule applies to various web server platforms, including Nginx, Apache, Apache Tomcat, IIS, and Traefik. This activity is significant for defenders because successful reconnaissance can precede more severe attacks, such as data exfiltration or system compromise, by revealing exploitable vulnerabilities. The rule is designed to trigger when the number of 5xx errors exceeds a defined threshold within a specified time interval.\u003c/p\u003e\n\u003ch2 id=\"attack-chain\"\u003eAttack Chain\u003c/h2\u003e\n\u003col\u003e\n\u003cli\u003eThe attacker initiates a reconnaissance phase by sending a series of HTTP GET requests to the target web server.\u003c/li\u003e\n\u003cli\u003eThe attacker uses vulnerability scanning tools to probe for known weaknesses in the web application, generating various types of requests, including invalid or malformed URLs.\u003c/li\u003e\n\u003cli\u003eThe web server processes each request, and those that encounter errors (e.g., invalid input, non-existent pages, server-side exceptions) result in 5xx error codes.\u003c/li\u003e\n\u003cli\u003eA high volume of these error responses are generated over a short period if the scanning tool aggressively probes the web server.\u003c/li\u003e\n\u003cli\u003eThe attacker analyzes the error responses to identify potential vulnerabilities or misconfigurations.\u003c/li\u003e\n\u003cli\u003eThe attacker may use identified vulnerabilities to perform additional scans or attempt to exploit the system.\u003c/li\u003e\n\u003cli\u003eIf successful, the attacker gains unauthorized access to the web server or underlying system.\u003c/li\u003e\n\u003cli\u003eThe attacker may proceed to further escalate privileges, install malware, or exfiltrate sensitive data.\u003c/li\u003e\n\u003c/ol\u003e\n\u003ch2 id=\"impact\"\u003eImpact\u003c/h2\u003e\n\u003cp\u003eA successful reconnaissance campaign can lead to the discovery of vulnerabilities that allow attackers to compromise web servers. This can result in data breaches, service disruptions, and reputational damage. While the error spike itself is a low-severity indicator, it can be a precursor to more critical attacks. The number of affected systems can range from a single server to an entire infrastructure, depending on the scope of the attacker's reconnaissance.\u003c/p\u003e\n\u003ch2 id=\"recommendation\"\u003eRecommendation\u003c/h2\u003e\n\u003cul\u003e\n\u003cli\u003eDeploy the Sigma rule \u0026quot;Web Server Potential Error Response Spike\u0026quot; to your SIEM to detect unusual spikes in 5xx error codes (rule.name).\u003c/li\u003e\n\u003cli\u003eInvestigate any alerts generated by the Sigma rule, focusing on the source IP addresses and requested URLs to identify potential scanners (rule.note).\u003c/li\u003e\n\u003cli\u003eImplement rate limiting and blocking mechanisms at the edge (e.g., reverse proxy, WAF) to mitigate identified malicious traffic (rule.note).\u003c/li\u003e\n\u003cli\u003eReview web server and application logs for patterns indicative of vulnerability scanning or fuzzing attempts, paying attention to User-Agent strings and request parameters (rule.note).\u003c/li\u003e\n\u003c/ul\u003e\n","date_modified":"2024-01-23T12:00:00Z","date_published":"2024-01-23T12:00:00Z","id":"https://feed.craftedsignal.io/briefs/2024-01-web-server-error-spike/","summary":"An unusual spike in web server error codes (500, 502, 503, 504) may indicate reconnaissance activities like vulnerability scanning or fuzzing, where attackers probe for weaknesses, potentially leading to exploitation of server-side issues.","title":"Web Server Error Response Spike Indicating Reconnaissance","url":"https://feed.craftedsignal.io/briefs/2024-01-web-server-error-spike/"},{"_cs_actors":[],"_cs_cpes":[],"_cs_cves":[],"_cs_exploited":false,"_cs_has_poc":false,"_cs_poc_references":[],"_cs_products":["Nginx","Apache HTTP Server","Apache Tomcat","IIS","Traefik"],"_cs_severities":["low"],"_cs_tags":["web-server","fuzzing","reconnaissance","web"],"_cs_type":"advisory","_cs_vendors":["Nginx","Apache","Microsoft","Traefik Labs"],"content_html":"\u003cp\u003eThis detection rule identifies potential web server discovery or fuzzing activity. Attackers often employ automated tools to discover hidden or unlinked resources on a web server. This reconnaissance phase involves sending a high volume of HTTP GET requests, often resulting in 404 (Not Found) or 403 (Forbidden) status codes. The rule focuses on identifying a single source IP address generating a large number of such requests within a defined timeframe. The targeted web servers can be running Nginx, Apache, Apache Tomcat, IIS, or Traefik. Detecting this activity early can prevent more targeted attacks by identifying and blocking malicious sources before they discover sensitive information or vulnerabilities. This proactive approach helps maintain the security and integrity of web applications and infrastructure.\u003c/p\u003e\n\u003ch2 id=\"attack-chain\"\u003eAttack Chain\u003c/h2\u003e\n\u003col\u003e\n\u003cli\u003e\u003cstrong\u003eInitial Reconnaissance:\u003c/strong\u003e The attacker begins by identifying potential target web servers.\u003c/li\u003e\n\u003cli\u003e\u003cstrong\u003eTool Selection:\u003c/strong\u003e The attacker chooses a web server discovery or fuzzing tool.\u003c/li\u003e\n\u003cli\u003e\u003cstrong\u003eRequest Generation:\u003c/strong\u003e The attacker uses the selected tool to generate a high volume of HTTP GET requests.\u003c/li\u003e\n\u003cli\u003e\u003cstrong\u003eResource Enumeration:\u003c/strong\u003e The tool iterates through a list of potential resource paths and sends GET requests to each.\u003c/li\u003e\n\u003cli\u003e\u003cstrong\u003eStatus Code Analysis:\u003c/strong\u003e The attacker analyzes the HTTP response codes to identify resources that return 404 or 403 status codes, indicating non-existent or forbidden paths.\u003c/li\u003e\n\u003cli\u003e\u003cstrong\u003eDiscovery of Hidden Resources:\u003c/strong\u003e The attacker identifies potentially vulnerable or misconfigured resources based on the responses.\u003c/li\u003e\n\u003cli\u003e\u003cstrong\u003eTargeted Exploitation:\u003c/strong\u003e The attacker focuses on the discovered resources, attempting to exploit vulnerabilities or gain unauthorized access.\u003c/li\u003e\n\u003cli\u003e\u003cstrong\u003eImpact:\u003c/strong\u003e Successful exploitation can lead to data breaches, system compromise, or other malicious activities.\u003c/li\u003e\n\u003c/ol\u003e\n\u003ch2 id=\"impact\"\u003eImpact\u003c/h2\u003e\n\u003cp\u003eSuccessful web server discovery and fuzzing can lead to the identification of sensitive files, misconfigured directories, and exploitable vulnerabilities. While this rule is rated as low severity, successful reconnaissance paves the way for more severe attacks. Exploitation of discovered vulnerabilities could lead to data breaches, unauthorized access, and denial-of-service attacks. The number of victims can vary depending on the scale and nature of the targeted web application. Sectors commonly targeted include e-commerce, banking, and government.\u003c/p\u003e\n\u003ch2 id=\"recommendation\"\u003eRecommendation\u003c/h2\u003e\n\u003cul\u003e\n\u003cli\u003eDeploy the Sigma rule \u003ccode\u003eWeb Server Fuzzing Activity - High Volume\u003c/code\u003e to your SIEM to detect suspicious IP addresses generating a high number of 404/403 responses (rule definition below).\u003c/li\u003e\n\u003cli\u003eReview web server logs for anomalies and unexpected 404/403 responses, focusing on the IP addresses flagged by the \u003ccode\u003eWeb Server Fuzzing Activity - High Volume\u003c/code\u003e rule.\u003c/li\u003e\n\u003cli\u003eImplement rate limiting on web servers to mitigate the impact of fuzzing attempts.\u003c/li\u003e\n\u003cli\u003eMonitor authentication logs for unusual patterns following the detection of web server fuzzing to catch potential exploitation attempts (related to the investigation steps).\u003c/li\u003e\n\u003cli\u003eBlock identified malicious IP addresses at the firewall or WAF (based on source.ip in the rule definition).\u003c/li\u003e\n\u003cli\u003eEnable comprehensive web server logging, including request methods, URLs, and response codes, to enhance detection capabilities.\u003c/li\u003e\n\u003c/ul\u003e\n","date_modified":"2024-01-09T12:00:00Z","date_published":"2024-01-09T12:00:00Z","id":"https://feed.craftedsignal.io/briefs/2024-01-09-web-fuzzing-recon/","summary":"This rule detects potential web server discovery or fuzzing activity by identifying a high volume of HTTP GET requests resulting in 404 or 403 status codes from a single source IP address within a short timeframe, indicating attackers discovering hidden resources for targeted attacks.","title":"Web Server Discovery or Fuzzing Activity Detection","url":"https://feed.craftedsignal.io/briefs/2024-01-09-web-fuzzing-recon/"},{"_cs_actors":[],"_cs_cpes":[],"_cs_cves":[],"_cs_exploited":false,"_cs_has_poc":false,"_cs_poc_references":[],"_cs_products":["Nginx","Apache HTTP Server","Apache Tomcat","Internet Information Services","Traefik"],"_cs_severities":["low"],"_cs_tags":["web-server","fuzzing","reconnaissance","web-application"],"_cs_type":"advisory","_cs_vendors":["Nginx","Apache Software Foundation","Microsoft","Traefik Labs"],"content_html":"\u003cp\u003eThis rule detects potential reconnaissance activity against web servers, specifically web server discovery or fuzzing. The activity is characterized by a single source IP address generating a high volume of HTTP GET requests that result in 404 (Not Found) or 403 (Forbidden) status codes within a short time period. The logic is based on analysis of web server logs from Nginx, Apache, Apache Tomcat, IIS, and Traefik. Such patterns typically indicate an attacker is trying to discover hidden or unlinked resources, potentially identifying vulnerabilities or sensitive information disclosure points on the web server. This discovery phase can often precede more targeted attacks. The detection logic triggers when more than 500 events from a single source IP are observed, involving more than 250 distinct URL requests.\u003c/p\u003e\n\u003ch2 id=\"attack-chain\"\u003eAttack Chain\u003c/h2\u003e\n\u003col\u003e\n\u003cli\u003eThe attacker initiates a connection to the target web server using an automated tool.\u003c/li\u003e\n\u003cli\u003eThe attacker sends a large number of HTTP GET requests to the web server, probing various URLs and paths.\u003c/li\u003e\n\u003cli\u003eThe web server responds to the requests, often returning 404 (Not Found) or 403 (Forbidden) status codes for non-existent or restricted resources.\u003c/li\u003e\n\u003cli\u003eThe attacker analyzes the HTTP response codes to identify potentially accessible or vulnerable resources.\u003c/li\u003e\n\u003cli\u003eIf accessible resources are found (e.g., administrative interfaces, backup files), the attacker attempts to access them.\u003c/li\u003e\n\u003cli\u003eThe attacker may attempt further exploitation based on discovered vulnerabilities or accessible resources.\u003c/li\u003e\n\u003cli\u003eThe attacker gains unauthorized access to the web server or sensitive data.\u003c/li\u003e\n\u003cli\u003eThe attacker performs malicious activities such as data theft, defacement, or system compromise.\u003c/li\u003e\n\u003c/ol\u003e\n\u003ch2 id=\"impact\"\u003eImpact\u003c/h2\u003e\n\u003cp\u003eSuccessful web server discovery and fuzzing can lead to the identification of sensitive files (e.g., configuration files, backups), vulnerable endpoints (e.g., administrative interfaces), and insecure configurations. An attacker can leverage this information to gain unauthorized access, leading to data breaches, system compromise, or service disruption. The severity of the impact depends on the nature of the exposed resources and the attacker's capabilities.\u003c/p\u003e\n\u003ch2 id=\"recommendation\"\u003eRecommendation\u003c/h2\u003e\n\u003cul\u003e\n\u003cli\u003eDeploy the Sigma rule \u003ccode\u003eWeb Server Fuzzing Detection\u003c/code\u003e to your SIEM and tune the threshold based on your environment's baseline traffic to reduce false positives.\u003c/li\u003e\n\u003cli\u003eReview web server logs for patterns matching the description in the \u003ccode\u003eOverview\u003c/code\u003e to identify potential attackers.\u003c/li\u003e\n\u003cli\u003eImplement rate limiting on your web servers and WAF to mitigate the impact of web server discovery and fuzzing attempts, based on the analysis of \u003ccode\u003ehttp.request.method\u003c/code\u003e and \u003ccode\u003ehttp.response.status_code\u003c/code\u003e.\u003c/li\u003e\n\u003cli\u003eEnsure that sensitive files and directories are properly secured and not publicly accessible, reviewing access control configurations on the web server.\u003c/li\u003e\n\u003cli\u003eMonitor web server logs for requests to common sensitive paths (e.g., /.env, /.git, /admin), using a rule targeting the \u003ccode\u003eurl.original\u003c/code\u003e field, to detect unauthorized access attempts.\u003c/li\u003e\n\u003c/ul\u003e\n","date_modified":"2024-01-02T12:00:00Z","date_published":"2024-01-02T12:00:00Z","id":"https://feed.craftedsignal.io/briefs/2024-01-web-server-fuzzing/","summary":"Detection of web server discovery or fuzzing activity indicated by a high volume of HTTP GET requests resulting in 404 or 403 status codes originating from a single source IP address within a short timeframe, suggesting attempts to discover hidden resources.","title":"Web Server Discovery or Fuzzing Activity Detected","url":"https://feed.craftedsignal.io/briefs/2024-01-web-server-fuzzing/"},{"_cs_actors":[],"_cs_cpes":[],"_cs_cves":[],"_cs_exploited":false,"_cs_has_poc":false,"_cs_poc_references":[],"_cs_products":["Nginx","Apache HTTP Server","Apache Tomcat","Internet Information Services","Traefik"],"_cs_severities":["low"],"_cs_tags":["reconnaissance","web-server","fuzzing"],"_cs_type":"advisory","_cs_vendors":["Nginx","Apache","Microsoft","Traefik Labs"],"content_html":"\u003cp\u003eThis detection identifies web server reconnaissance and fuzzing attempts. The rule is triggered when a single source IP address generates a high volume of HTTP GET requests that result in 404 (Not Found) or 403 (Forbidden) status codes within a short period. This behavior suggests an attacker is trying to discover hidden or unlinked resources on a web server, a common initial step before more targeted attacks. This is achieved by counting events and distinct URLs accessed from logs across Nginx, Apache, Apache Tomcat, IIS, and Traefik web servers. The rule triggers if more than 500 events and 250 distinct URLs are observed from a single IP address within the monitored timeframe.\u003c/p\u003e\n\u003ch2 id=\"attack-chain\"\u003eAttack Chain\u003c/h2\u003e\n\u003col\u003e\n\u003cli\u003eThe attacker initiates network connections to a target web server (Nginx, Apache, etc.).\u003c/li\u003e\n\u003cli\u003eThe attacker sends a series of HTTP GET requests to various URLs, often using a wordlist.\u003c/li\u003e\n\u003cli\u003eThe web server processes each request and returns HTTP status codes.\u003c/li\u003e\n\u003cli\u003eThe attacker analyzes the HTTP status codes to identify existing resources.\u003c/li\u003e\n\u003cli\u003eA large number of 404 (Not Found) or 403 (Forbidden) responses indicate a fuzzing attempt.\u003c/li\u003e\n\u003cli\u003eThe attacker identifies potentially vulnerable or misconfigured resources.\u003c/li\u003e\n\u003cli\u003eThe attacker may attempt to exploit discovered vulnerabilities.\u003c/li\u003e\n\u003cli\u003eSuccessful exploitation could lead to information disclosure or unauthorized access.\u003c/li\u003e\n\u003c/ol\u003e\n\u003ch2 id=\"impact\"\u003eImpact\u003c/h2\u003e\n\u003cp\u003eSuccessful web server discovery enables attackers to map out a web application's structure and identify potential vulnerabilities or misconfigurations. This reconnaissance can precede more severe attacks, such as unauthorized access to sensitive data, code execution, or denial-of-service attacks. While this rule has low severity, successful reconnaissance can lead to high impact outcomes.\u003c/p\u003e\n\u003ch2 id=\"recommendation\"\u003eRecommendation\u003c/h2\u003e\n\u003cul\u003e\n\u003cli\u003eDeploy the Sigma rule \u003ccode\u003eHigh Volume of 404/403 GET Requests\u003c/code\u003e to your SIEM and tune the threshold (events \u0026gt; 500 and URLs \u0026gt; 250) for your environment.\u003c/li\u003e\n\u003cli\u003eInvestigate any alerts generated by the Sigma rule to identify the source IP address and the target web server, then check the associated logs.\u003c/li\u003e\n\u003cli\u003eReview WAF/CDN logs for rate limiting and blocks related to the suspicious source IP, as recommended in the overview.\u003c/li\u003e\n\u003cli\u003eImplement rate limiting on web servers to mitigate the impact of web server discovery and fuzzing attempts, as mentioned in the overview.\u003c/li\u003e\n\u003cli\u003eHarden the web tier by disabling directory listing and default app endpoints, blocking patterns like /.git/, /.env, and /backup.zip at the WAF, and restricting origin access to CDN egress only, as mentioned in the overview.\u003c/li\u003e\n\u003c/ul\u003e\n","date_modified":"2024-01-02T12:00:00Z","date_published":"2024-01-02T12:00:00Z","id":"https://feed.craftedsignal.io/briefs/2024-01-web-server-recon/","summary":"Detection of potential web server discovery or fuzzing activity characterized by a high volume of HTTP GET requests resulting in 404 or 403 status codes originating from a single source IP address within a short timeframe, indicating attackers are probing for hidden resources.","title":"Web Server Discovery or Fuzzing Activity","url":"https://feed.craftedsignal.io/briefs/2024-01-web-server-recon/"}],"language":"en","title":"CraftedSignal Threat Feed - Fuzzing","version":"https://jsonfeed.org/version/1.1"}