ATT&CK coverage › Technique

Pre-OS Boot: Bootkit T1542.003

Adversaries may use bootkits to persist on systems. A bootkit is a malware variant that modifies the boot sectors of a hard drive, allowing malicious code to execute before a computer's operating system has loaded. Bootkits reside at a layer below the operating system and may make it difficult to perform full remediation unless an organization suspects one was used and can act accordingly.

Events covered

2 catalog events are tagged with this technique by at least one rule.

ProviderEvent IDTitle
Sysmon1Process creation
Sysmon3Network connection

Authoring guide

Patterns shared across the 2 rules above: which fields they filter on, what specific values they look for, and what they exclude. Field names are normalized across vendors so Sigma's Image, Elastic's process.name, and Splunk's process_name collapse into one row. Each rule contributes at most once per row.

Fields filtered most (5 distinct)

The fields most rules look at when detecting this technique. The How column shows the operators authors use (eq, wildcard, regex_match, match) and how often each appears. Sample values are concrete examples to start from, not an exhaustive list.

FieldRulesHowSample values
CommandLine2match 1, ne 1network, import, safeboot, unknown
Image1ends_with 1\bcdedit.exe
OriginalFileName1eq 1bcdedit.exe
process_name1eq 1winlogon.exe
DestinationPort1ne 10

Top indicator values (10 distinct)

Specific (field, operator, value) combinations the rules check for, ranked by how many rules under this technique use each one. The Corpus reach column counts how many rules across the entire catalog (any technique) check the same combination. High numbers point to widely-used indicators that are likely noisy on their own; combine them with another condition for useful signal. Blank means the combination is specific to rules under this technique.

FieldKindValueRules (here)Corpus reach
CommandLinematchdelete17
CommandLinematchdeletevalue1
OriginalFileNameeqbcdedit.exe12
Imageends_with\bcdedit.exe14
CommandLinematchsafeboot1
CommandLinematchimport12
CommandLinematchnetwork1
CommandLineneunknown12
process_nameeqwinlogon.exe1
DestinationPortne016

Common exclusions (5 distinct)

Field/operator/value combinations that rules under this technique routinely exclude (top-level not() clauses). These are the false-positive paths the community has learned to filter out. A new rule that ignores the high-count entries here will likely fire on the same noisy paths.

FieldKindValueRules excluding
All_Traffic.destin10.0.0.0/81
All_Traffic.destin172.16.0.0/121
All_Traffic.destin127.0.0.11
All_Traffic.destin192.168.0.0/161
All_Traffic.destin0:0:0:0:0:0:0:11

Rules under this technique

Every rule in the catalog tagged with this technique, grouped by vendor. Click a rule title for its full predicates, exclusions, and indicators.

Sigma 1 rule

Splunk 1 rule