Newly Observed FortiGate Alert

 1[metadata]
 2creation_date = "2026/01/21"
 3integration = ["fortinet_fortigate"]
 4maturity = "production"
 5updated_date = "2026/01/21"
 6
 7[rule]
 8author = ["Elastic"]
 9description = """
10This rule detects FortiGate alerts that are observed for the first time in the previous 5 days of alert history.
11Analysts can use this to prioritize triage and response.
12"""
13from = "now-7205m"
14interval = "5m"
15language = "esql"
16license = "Elastic License v2"
17name = "Newly Observed FortiGate Alert"
18risk_score = 99
19rule_id = "2c40dfe2-c13e-48a8-8eff-fb9bfb2a7854"
20severity = "critical"
21tags = ["Use Case: Threat Detection", "Rule Type: Higher-Order Rule", "Resources: Investigation Guide", "Domain: Network", "Data Source: Fortinet"]
22timestamp_override = "event.ingested"
23type = "esql"
24
25query = '''
26FROM logs-fortinet_fortigate.*, filebeat-* metadata _id
27
28| WHERE event.module == "fortinet_fortigate" and event.action in ("signature", "ssl-anomaly") and
29  message is not null and event.category != "authentication" and
30  message != "Connection Failed" and not message like "Web.Client: *" and
31  not message like "Network.Service: *" and not message like "General.Interest*" and not message like "Update: *"
32
33| STATS Esql.alerts_count = count(*),
34        Esql.first_time_seen = MIN(@timestamp),
35        Esql.distinct_count_src_ip = COUNT_DISTINCT(source.ip),
36        Esql.distinct_count_dst_ip = COUNT_DISTINCT(destination.ip),
37        src_ip = VALUES(source.ip),
38        dst_ip = VALUES(destination.ip),
39        url_domain = VALUES(url.domain),
40        url_path = VALUES(url.path) by message, event.category, event.outcome
41
42// first time seen is within 10m of the rule execution time
43| eval Esql.recent = DATE_DIFF("minute", Esql.first_time_seen, now())
44| where Esql.recent <= 10 and Esql.alerts_count <= 5 and Esql.distinct_count_src_ip <= 2 and Esql.distinct_count_dst_ip <= 2
45
46// move dynamic fields to ECS equivalent for rule exceptions
47| eval source.ip = MV_FIRST(src_ip),
48       destination.ip = MV_FIRST(dst_ip),
49       url.domain = MV_FIRST(url_domain),
50       url.path = MV_FIRST(url_path)
51
52| keep message, event.category, event.outcome, Esql.*, source.ip, destination.ip, url.domain, url.path
53'''
54note = """## Triage and analysis
55
56### Investigating Newly Observed Fortigate Alert
57
58This rule surfaces newly observed, low-frequency high severity FortiGate alerts within the last 5 days.
59
60Because the alert has not been seen previously, it should be prioritized for validation to determine whether it represents a true compromise or rare benign activity.
61
62### Investigation Steps
63
64- Identify the source address, affected host and review the associated message to understand the alert.
65- Validate the source address under which the activity occurred and assess whether it aligns with normal behavior.
66- Refer to the specific alert details like event.original to get more context.
67
68### False Positive Considerations
69
70- Vulnerability scanners and pentesting.
71- Administrative scripts or automation tools can trigger detections when first introduced.
72- Development or testing environments may produce one-off behaviors that resemble malicious techniques.
73
74### Response and Remediation
75
76- If the activity is confirmed malicious, isolate the affected host to prevent further execution or lateral movement.
77- Terminate malicious processes and remove any dropped files or persistence mechanisms.
78- Collect forensic artifacts to understand initial access and execution flow.
79- Patch or remediate any vulnerabilities or misconfigurations that enabled the behavior.
80- If benign, document the finding and consider tuning or exception handling to reduce future noise.
81- Continue monitoring the host and environment for recurrence of the behavior or related alerts."""
82references = ["https://www.elastic.co/docs/reference/integrations/fortinet_fortigate"]