mirror of
https://github.com/splunk/security_content
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Michael Haag
67 lines
3.1 KiB
YAML
67 lines
3.1 KiB
YAML
name: SSL Certificates with Punycode
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id: 696694df-5706-495a-81f2-79501fa11b90
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version: 1
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date: '2022-11-01'
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author: Michael Haag, Splunk
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type: Hunting
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datamodel: []
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description: The following analytic utilizes the Certificates Datamodel to look for punycode domains, starting with xn--, found in the SSL issuer email domain.
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The presence of punycode here does not equate to evil, therefore we need to decode the punycode to determine what it translates to. Remove the CyberChef recipe as needed and decode manually.
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Note that this is not the exact location of the malicious punycode to trip CVE-2022-3602, but a method to at least identify fuzzing occurring on these email paths.
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What does evil look like? it will start with
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search: '| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time)
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as lastTime from datamodel=Certificates.All_Certificates by All_Certificates.SSL.ssl_issuer_email_domain All_Certificates.SSL.ssl_issuer All_Certificates.SSL.ssl_subject_email All_Certificates.SSL.dest All_Certificates.SSL.src All_Certificates.SSL.sourcetype All_Certificates.SSL.ssl_subject_email_domain
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| `drop_dm_object_name("All_Certificates.SSL")`
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| eval punycode=if(like(ssl_issuer_email_domain,"%xn--%"),1,0)
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| where punycode=1
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| cyberchef infield="ssl_issuer_email_domain" outfield="convertedPuny" jsonrecipe="[{"op":"From Punycode","args":[true]}]"
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| table ssl_issuer_email_domain convertedPuny ssl_issuer ssl_subject_email dest src sourcetype ssl_subject_email_domain
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| `ssl_certificates_with_punycode_filter`'
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how_to_implement: Ensure data is properly being ingested into the Certificates datamodel. If decoding the of interest, the CyberChef app is needed https://splunkbase.splunk.com/app/5348. If decoding is not needed, remove the cyberchef lines.
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known_false_positives: False positives may be present if the organization works with international businesses. Filter as needed.
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references:
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- https://www.splunk.com/en_us/blog/security/nothing-puny-about-cve-2022-3602.html
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- https://www.openssl.org/blog/blog/2022/11/01/email-address-overflows/
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- https://community.emergingthreats.net/t/out-of-band-ruleset-update-summary-2022-11-01/117
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- https://github.com/corelight/CVE-2022-3602/tree/master/scripts
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tags:
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analytic_story:
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- OpenSSL CVE-2022-3602
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asset_type: Network
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cis20:
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- CIS 3
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- CIS 5
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- CIS 16
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confidence: 30
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context:
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- Source:IPS
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dataset: []
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impact: 50
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kill_chain_phases:
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- Reconnaissance
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- Delivery
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message: A x509 certificate has been identified to have punycode in the SSL issuer email domain on $dest$.
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mitre_attack_id:
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- T1573
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nist:
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- DE.CM
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observable:
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- name: dest
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type: Hostname
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role:
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- Victim
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product:
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- Splunk Enterprise
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- Splunk Enterprise Security
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- Splunk Cloud
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required_fields:
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- All_Certificates.SSL.ssl_issuer_email_domain
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- All_Certificates.SSL.ssl_issuer
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- All_Certificates.SSL.ssl_subject_email
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- All_Certificates.SSL.dest
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- All_Certificates.SSL.src
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- All_Certificates.SSL.sourcetype
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- All_Certificates.SSL.ssl_subject_email_domain
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risk_score: 15
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security_domain: network
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