{"description":"Trending threats, MITRE ATT\u0026CK coverage, and detection metadata. Fed continuously.","feed_url":"https://feed.craftedsignal.io/products/fortigate-ssl-vpn/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":["Fortigate SSL VPN"],"_cs_severities":["medium"],"_cs_tags":["fortigate","sslvpn","initial-access","siem"],"_cs_type":"advisory","_cs_vendors":["Fortinet"],"content_html":"\u003cp\u003eThis brief focuses on detecting potential malicious activity following a successful Fortigate SSL VPN login. The alert is triggered when a user successfully logs in to the Fortigate SSL VPN and is subsequently flagged by a SIEM system, indicating suspicious or anomalous behavior after gaining network access. This could signify a compromised account being used for malicious purposes or an attacker leveraging VPN access for lateral movement and data exfiltration. Defenders should investigate these alerts promptly to identify and contain potential breaches. The detection is based on observing VPN logins in conjunction with other security alerts generated by the SIEM.\u003c/p\u003e\n\u003ch2 id=\"attack-chain\"\u003eAttack Chain\u003c/h2\u003e\n\u003col\u003e\n\u003cli\u003eAttacker gains credentials through phishing or credential stuffing (Hypothetical).\u003c/li\u003e\n\u003cli\u003eAttacker successfully authenticates to the Fortigate SSL VPN using the compromised credentials.\u003c/li\u003e\n\u003cli\u003eInitial access to the internal network is established via the VPN tunnel.\u003c/li\u003e\n\u003cli\u003eAttacker performs reconnaissance activities, such as network scanning and enumeration, potentially using tools like Nmap or Bloodhound.\u003c/li\u003e\n\u003cli\u003eMalicious activity triggers a SIEM alert (e.g., unusual file access, suspicious process creation, or lateral movement).\u003c/li\u003e\n\u003cli\u003eThe attacker attempts to escalate privileges on compromised systems using exploits or credential dumping tools like Mimikatz (Hypothetical).\u003c/li\u003e\n\u003cli\u003eAttacker moves laterally within the network to gain access to sensitive data or critical systems.\u003c/li\u003e\n\u003cli\u003eData exfiltration is initiated using tools like rclone or scp (Hypothetical), or ransomware is deployed.\u003c/li\u003e\n\u003c/ol\u003e\n\u003ch2 id=\"impact\"\u003eImpact\u003c/h2\u003e\n\u003cp\u003eA successful attack following a Fortigate SSL VPN login can lead to significant consequences, including data breaches, financial losses, and reputational damage. By compromising a VPN account, attackers can bypass network perimeter security and gain access to sensitive internal resources. The impact can range from unauthorized access to sensitive data to the complete disruption of business operations through ransomware deployment. Targeted sectors could include any organization relying on Fortigate SSL VPN for remote access.\u003c/p\u003e\n","date_modified":"2024-01-30T12:00:00Z","date_published":"2024-01-30T12:00:00Z","id":"https://feed.craftedsignal.io/briefs/2024-01-30-fortigate-ssl-vpn-siem-alert/","summary":"Detection of initial access via Fortigate SSL VPN login, followed by a SIEM alert, indicating potential malicious activity post-VPN access.","title":"Fortigate SSL VPN Login Followed by SIEM Alert","url":"https://feed.craftedsignal.io/briefs/2024-01-30-fortigate-ssl-vpn-siem-alert/"},{"_cs_actors":[],"_cs_cpes":[],"_cs_cves":[],"_cs_exploited":false,"_cs_has_poc":false,"_cs_poc_references":[],"_cs_products":["FortiGate SSL VPN"],"_cs_severities":["medium"],"_cs_tags":["fortinet","vpn","initial-access","credential-access"],"_cs_type":"advisory","_cs_vendors":["Fortinet"],"content_html":"\u003cp\u003eThis detection rule identifies instances where a user successfully logs into a FortiGate SSL VPN and is subsequently flagged by a SIEM alert within a 10-minute window. This sequence of events can indicate a compromised account being used to access the network remotely, followed by malicious activity triggering the SIEM. It can also highlight legitimate users engaging in risky behavior after establishing a VPN connection. The rule focuses on FortiGate SSL VPN events (event codes \u0026quot;0101039426\u0026quot; and \u0026quot;0101039427\u0026quot;) correlated with any subsequent SIEM alert (excluding alerts originating from FortiGate logs or the correlation rule itself) with a risk score greater than 21. This correlation helps defenders quickly identify potentially malicious VPN usage. The original rule was published on 2026-03-23.\u003c/p\u003e\n\u003ch2 id=\"attack-chain\"\u003eAttack Chain\u003c/h2\u003e\n\u003col\u003e\n\u003cli\u003eAn attacker gains unauthorized access to valid user credentials through phishing, credential stuffing, or other means (T1078).\u003c/li\u003e\n\u003cli\u003eThe attacker uses the compromised credentials to successfully log in to a FortiGate SSL VPN, triggering a Fortinet authentication log event (event code \u0026quot;0101039426\u0026quot; or \u0026quot;0101039427\u0026quot;).\u003c/li\u003e\n\u003cli\u003eAfter gaining VPN access, the attacker attempts to move laterally within the network (T1021).\u003c/li\u003e\n\u003cli\u003eThe attacker executes malicious code on an internal system, such as a PowerShell script or a Cobalt Strike beacon (T1059).\u003c/li\u003e\n\u003cli\u003eThe malicious activity triggers a SIEM alert due to suspicious behavior like unusual network connections, file modifications, or registry changes (T1562).\u003c/li\u003e\n\u003cli\u003eThe SIEM alert is correlated with the preceding FortiGate VPN login based on the username within a 10-minute timeframe.\u003c/li\u003e\n\u003cli\u003eThe attacker establishes persistence on the compromised system (T1547).\u003c/li\u003e\n\u003cli\u003eThe attacker proceeds with their objectives, such as data exfiltration or ransomware deployment (TA0011).\u003c/li\u003e\n\u003c/ol\u003e\n\u003ch2 id=\"impact\"\u003eImpact\u003c/h2\u003e\n\u003cp\u003eA successful attack following this pattern can lead to significant damage, including data breaches, financial losses, and reputational damage. Compromised VPN access provides attackers with a privileged entry point into the internal network, allowing them to bypass perimeter security controls. Depending on the permissions of the compromised user, the attacker may be able to access sensitive data, disrupt critical systems, and move laterally to other high-value targets within the organization.\u003c/p\u003e\n\u003ch2 id=\"recommendation\"\u003eRecommendation\u003c/h2\u003e\n\u003cul\u003e\n\u003cli\u003eDeploy the provided Sigma rule to your SIEM to detect FortiGate SSL VPN logins followed by SIEM alerts. Tune the rule's \u003ccode\u003emaxspan\u003c/code\u003e and \u003ccode\u003erisk_score\u003c/code\u003e thresholds to reduce false positives based on your environment.\u003c/li\u003e\n\u003cli\u003eInvestigate any alerts generated by the Sigma rule, focusing on the activities performed by the user after the VPN login. Use the \u0026quot;Investigation Guide\u0026quot; tag in the original rule as a starting point for analysis.\u003c/li\u003e\n\u003cli\u003eReview FortiGate logs for unusual login patterns, such as logins from unfamiliar geographic locations or multiple failed login attempts followed by a successful login.\u003c/li\u003e\n\u003cli\u003eImplement multi-factor authentication (MFA) for all VPN users to reduce the risk of credential compromise.\u003c/li\u003e\n\u003cli\u003eMonitor SIEM alerts for indicators of lateral movement, such as unusual network connections, privilege escalation attempts, and suspicious process executions.\u003c/li\u003e\n\u003c/ul\u003e\n","date_modified":"2024-01-03T12:00:00Z","date_published":"2024-01-03T12:00:00Z","id":"https://feed.craftedsignal.io/briefs/2024-01-fortigate-vpn-siem-alert/","summary":"Detects FortiGate SSL VPN logins followed by a SIEM detection alert for the same user within a short timeframe, potentially indicating VPN abuse, credential compromise, or initial access followed by post-compromise activity.","title":"FortiGate SSL VPN Login Followed by SIEM Alert","url":"https://feed.craftedsignal.io/briefs/2024-01-fortigate-vpn-siem-alert/"}],"language":"en","title":"CraftedSignal Threat Feed - FortiGate SSL VPN","version":"https://jsonfeed.org/version/1.1"}