Query: alert when 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 a suspicious process creation as SYSTEM user (suspicious program or command line parameter). Logsource: windows / process_creation. Rule: title: Suspicious SYSTEM User Process Creation id: 2617e7ed-adb7-40ba-b0f3-8f9945fe6c09 status: test description: Detects a suspicious process creation as SYSTEM user (suspicious program or command line parameter) references: - Internal Research - https://tools.thehacker.recipes/mimikatz/modules author: Florian Roth (Nextron Systems), David ANDRE (additional keywords) date: 2021-12-20 modified: 2025-10-19 tags: - attack.credential-access - attack.privilege-escalation - attack.stealth - attack.t1134 - attack.t1003 - attack.t1027 logsource: category: process_creation product: windows detection: selection: IntegrityLevel: - System - S-1-16-16384 User|contains: - AUTHORI - AUTORI selection_special: - Image|endswith: - \calc.exe - \cscript.exe - \forfiles.exe - \hh.exe - \mshta.exe - \ping.exe - \wscript.exe - CommandLine|re: net\s+user\s+ - CommandLine|contains: - ' -NoP ' - ' -W Hidden ' - ' -decode ' - ' /decode ' - ' /urlcache ' - ' -urlcache ' - ' -e* JAB' - ' -e* SUVYI' - ' -e* SQBFAFgA' - ' -e* aWV4I' - ' -e* IAB' - ' -e* PAA' - ' -e* aQBlAHgA' - vssadmin delete shadows - reg SAVE HKLM - ' -ma ' - Microsoft\Windows\CurrentVersion\Run - .downloadstring( - .downloadfile( - ' /ticket:' - 'dpapi::' - event::clear - event::drop - id::modify - 'kerberos::' - 'lsadump::' - 'misc::' - 'privilege::' - 'rpc::' - 'sekurlsa::' - 'sid::' - 'token::' - vault::cred - vault::list - ' p::d ' - ;iex( - MiniDump filter_main_ping: CommandLine|contains|all: - ping - 127.0.0.1 - ' -n ' filter_vs: Image|endswith: \PING.EXE ParentCommandLine|contains: \DismFoDInstall.cmd filter_config_mgr: ParentImage|contains: :\Packages\Plugins\Microsoft.GuestConfiguration.ConfigurationforWindows\ filter_java: ParentImage|contains: - :\Program Files (x86)\Java\ - :\Program Files\Java\ ParentImage|endswith: \bin\javaws.exe Image|contains: - :\Program Files (x86)\Java\ - :\Program Files\Java\ Image|endswith: \bin\jp2launcher.exe CommandLine|contains: ' -ma ' condition: all of selection* and not 1 of filter_* falsepositives: - Administrative activity - Scripts and administrative tools used in the monitored environment - Monitoring activity level: high