Query: detection rule: The DNS Z flag is bit within the DNS protocol header that is, per the IETF design, meant to be used reserved (unused). A
Matching passage: Sigma rule: The DNS Z flag is bit within the DNS protocol header that is, per the IETF design, meant to be used reserved (unused). A. Logsource: zeek / dns. Rule: title: Suspicious DNS Z Flag Bit Set id: ede05abc-2c9e-4624-9944-9ff17fdc0bf5 status: test description: 'The DNS Z flag is bit within the DNS protocol header that is, per the IETF design, meant to be used reserved (unused). Although recently it has been used in DNSSec, the value being set to anything other than 0 should be rare. Otherwise if it is set to non 0 and DNSSec is being used, then excluding the legitimate domains is low effort and high reward. Determine if multiple of these files were accessed in a short period of time to further enhance the possibility of seeing if this was a one off or the possibility of larger sensitive file gathering. This Sigma query is designed to accompany the Corelight Threat Hunting Guide, which can be found here: https://www3.corelight.com/corelights-introductory-guide-to-threat-hunting-with-zeek-bro-logs'' ' references: - https://twitter.com/neu5ron/status/1346245602502443009 - https://tdm.socprime.com/tdm/info/eLbyj4JjI15v#sigma - https://tools.ietf.org/html/rfc2929#section-2.1 - https://www.netresec.com/?page=Blog&month=2021-01&post=Finding-Targeted-SUNBURST-Victims-with-pDNS author: '@neu5ron, SOC Prime Team, Corelight' date: 2021-05-04 modified: 2022-11-29 tags: - attack.t1095 - attack.t1571 - attack.command-and-control logsource: product: zeek service: dns detection: z_flag_unset: Z: 0 most_probable_valid_domain: query|contains: . exclude_tlds: query|endswith: - .arpa - .local - .ultradns.net - .twtrdns.net - .azuredns-prd.info - .azure-dns.com - .azuredns-ff.info - .azuredns-ff.org - .azuregov-dns.org exclude_query_types: qtype_name: - ns - mx exclude_responses: answers|endswith: \\x00 exclude_netbios: id.resp_p: - 137 - 138 - 139 condition: not z_flag_unset and most_probable_valid_domain and not (exclude_tlds or exclude_query_types or exclude_responses or exclude_netbios) falsepositives: - Internal or legitimate external domains using DNSSec. Verify if these are legitimate DNSSec domains and then exclude them. - If you work in a Public Sector then it may be good to exclude things like endswith ".edu", ".gov" and or ".mil" level: medium
Near-miss passage: Sigma rule: Detects the deletion of registry keys containing the MSTSC connection history. Logsource: windows / registry_delete. Rule: title: Terminal Server Client Connection History Cleared - Registry id: 07bdd2f5-9c58-4f38-aec8-e101bb79ef8d status: test description: Detects the deletion of registry keys containing the MSTSC connection history references: - https://learn.microsoft.com/en-us/troubleshoot/windows-server/remote/remove-entries-from-remote-desktop-connection-computer - http://woshub.com/how-to-clear-rdp-connections-history/ - https://www.trendmicro.com/en_us/research/23/a/vice-society-ransomware-group-targets-manufacturing-companies.html author: Christian Burkard (Nextron Systems) date: 2021-10-19 modified: 2023-02-08 tags: - attack.persistence - attack.stealth - attack.defense-impairment - attack.t1070 - attack.t1112 logsource: category: registry_delete product: windows detection: selection1: EventType: DeleteValue TargetObject|contains: \Microsoft\Terminal Server Client\Default\MRU selection2: EventType: DeleteKey TargetObject|contains: \Microsoft\Terminal Server Client\Servers\ condition: 1 of selection* falsepositives: - Unknown level: high