Brand impersonation: Microsoft logo or suspicious language with open redirect

Severity: high
Type: rule
Source: github.com/sublime-security/sublime-rules

Message contains a Microsoft logo or suspicious terms and use of an open redirect. This has been exploited in the wild to impersonate Microsoft.

Threat classification

Sublime's own taxonomy (not MITRE ATT&CK).

Category	Values
Attack types	BEC/Fraud
Tactics and techniques	Impersonation: Brand, Open redirect, Social engineering

Event coverage

Message attribute
attachments (collection)
body
body.links (collection)
headers (collection)
sender.email
type

Rule body MQL

type.inbound
and (length(attachments) < 5 or length(body.links) < 10)
// Microsoft logo
and (
  any(attachments,
      .file_type in $file_types_images
      and any(ml.logo_detect(.).brands, strings.starts_with(.name, "Microsoft"))
  )
  or any(attachments,
         .file_type in $file_types_images
         and (
           any(file.explode(.),
               2 of (
                 strings.ilike(.scan.ocr.raw, "*password*"),
                 strings.ilike(.scan.ocr.raw, "*unread messages*"),
                 strings.ilike(.scan.ocr.raw, "*Shared Documents*"),
                 strings.ilike(.scan.ocr.raw, "*expiration*"),
                 strings.ilike(.scan.ocr.raw, "*office*"),
                 strings.ilike(.scan.ocr.raw, "*expire*"),
                 strings.ilike(.scan.ocr.raw, "*expiring*"),
                 strings.ilike(.scan.ocr.raw, "*kindly*"),
                 strings.ilike(.scan.ocr.raw, "*renew*"),
                 strings.ilike(.scan.ocr.raw, "*review"),
                 strings.ilike(.scan.ocr.raw, "*emails failed*"),
                 strings.ilike(.scan.ocr.raw, "*kicked out*"),
                 strings.ilike(.scan.ocr.raw, "*prevented*"),
                 strings.ilike(.scan.ocr.raw, "*storage quota*"),
                 strings.ilike(.scan.ocr.raw, "*required now"),
                 strings.ilike(.scan.ocr.raw, "*cache*"),
                 strings.ilike(.scan.ocr.raw, "*qr code*"),
                 strings.ilike(.scan.ocr.raw, "*barcode*"),
                 strings.ilike(.scan.ocr.raw, "*security update*"),
                 strings.ilike(.scan.ocr.raw, "*quarantine*")
               )
           )
         )
  )
)

// open redirect
and any(body.links,
        any(.href_url.rewrite.encoders, strings.icontains(., "open_redirect"))
        and not .href_url.domain.root_domain in $org_domains
)
and not (length(headers.references) > 0 or headers.in_reply_to is not null)
and sender.email.domain.root_domain not in $org_domains
and sender.email.domain.root_domain not in (
  "bing.com",
  "microsoft.com",
  "microsoftonline.com",
  "microsoftstoreemail.com",
  "microsoftsupport.com",
  "microsoft365.com",
  "office.com",
  "onedrive.com",
  "sharepointonline.com",
  "yammer.com"
)

Detection logic

Scope: inbound message.

Message contains a Microsoft logo or suspicious terms and use of an open redirect. This has been exploited in the wild to impersonate Microsoft.

inbound message
any of:
- length(attachments) < 5
- length(body.links) < 10
any of:
- any of attachments where all hold:
  - .file_type in $file_types_images
  - any of ml.logo_detect(.).brands where:
    
    .name starts with 'Microsoft'
- any of attachments where all hold:
  - .file_type in $file_types_images
  - any of file.explode(.) where:
    
    at least 2 of 20: .scan.ocr.raw matches any of 20 patterns
    
    *password*
    *unread messages*
    *Shared Documents*
    *expiration*
    *office*
    *expire*
    *expiring*
    *kindly*
    *renew*
    *review
    *emails failed*
    *kicked out*
    *prevented*
    *storage quota*
    *required now
    *cache*
    *qr code*
    *barcode*
    *security update*
    *quarantine*
any of body.links where all hold:
- any of .href_url.rewrite.encoders where:
  - . contains 'open_redirect'
- not:
  - .href_url.domain.root_domain in $org_domains
none of:
- length(headers.references) > 0
- headers.in_reply_to is set
sender.email.domain.root_domain not in $org_domains
sender.email.domain.root_domain not in ('bing.com', 'microsoft.com', 'microsoftonline.com', 'microsoftstoreemail.com', 'microsoftsupport.com', 'microsoft365.com', 'office.com', 'onedrive.com', 'sharepointonline.com', 'yammer.com')

Inspects: attachments[].file_type, body.links, body.links[].href_url.domain.root_domain, body.links[].href_url.rewrite.encoders, headers.in_reply_to, headers.references, sender.email.domain.root_domain, type.inbound. Sensors: file.explode, ml.logo_detect, strings.icontains, strings.ilike, strings.starts_with. Reference lists: $file_types_images, $org_domains.

Indicators matched (32)

Field	Match	Value
`strings.starts_with`	prefix	`Microsoft`
`strings.ilike`	substring	`password`
`strings.ilike`	substring	`unread messages`
`strings.ilike`	substring	`Shared Documents`
`strings.ilike`	substring	`expiration`
`strings.ilike`	substring	`office`
`strings.ilike`	substring	`expire`
`strings.ilike`	substring	`expiring`
`strings.ilike`	substring	`kindly`
`strings.ilike`	substring	`renew`
`strings.ilike`	substring	`*review`
`strings.ilike`	substring	`emails failed`

20 more

`strings.ilike`	substring	`kicked out`
`strings.ilike`	substring	`prevented`
`strings.ilike`	substring	`storage quota`
`strings.ilike`	substring	`*required now`
`strings.ilike`	substring	`cache`
`strings.ilike`	substring	`qr code`
`strings.ilike`	substring	`barcode`
`strings.ilike`	substring	`security update`
`strings.ilike`	substring	`quarantine`
`strings.icontains`	substring	`open_redirect`
`sender.email.domain.root_domain`	member	`bing.com`
`sender.email.domain.root_domain`	member	`microsoft.com`
`sender.email.domain.root_domain`	member	`microsoftonline.com`
`sender.email.domain.root_domain`	member	`microsoftstoreemail.com`
`sender.email.domain.root_domain`	member	`microsoftsupport.com`
`sender.email.domain.root_domain`	member	`microsoft365.com`
`sender.email.domain.root_domain`	member	`office.com`
`sender.email.domain.root_domain`	member	`onedrive.com`
`sender.email.domain.root_domain`	member	`sharepointonline.com`
`sender.email.domain.root_domain`	member	`yammer.com`

`j` / `k`	Scroll down / up
`d` / `u`	Half-page down / up
`gg` / `G`	Top / bottom
`h` / `l`	History back / forward
`f`	Follow link (`Shift` = new tab)
`/`	Focus search
`?`	Toggle this help
`↑` / `↓`	Navigate search results
`Enter`	Open highlighted result
`Esc`	Close results / dialog

`type:`	`events` / `rules` / `providers`
`vendor:`	`sigma` / `elastic` / `splunk` / `kusto` / `chronicle` (vendor name alone also works: `sigma:`, `kql:`, `secops:`…)
`tactic:`	TA-id, slug, or name: `credential_access`, `TA0006`
`technique:`	technique or sub-technique ID: `T1003`, `T1003.001` (alias `tech:`)
`severity:`	`critical` / `high` / `medium` / `low` / `informational` (alias `sev:`)
`risk_score`	Numeric comparison on the Elastic risk score (0 to 100): `risk_score>50`, `risk_score<=20`, `risk_score=99` (alias `risk`; Elastic rules only)
`stages:`	Rules with exactly N pipeline stages
`correlation:`	`single_event` / `sequence` / `alternatives` / `alternatives_cross_log` / `all_required` / `correlated`
`with:`	Co-occurrence event-id; stacks (`with:4624 with:4769`) to require all, while a comma list in one occurrence (`with:4624,4769`) is an either-or group. Implies multi-event
`like:`	Structural neighbors of a rule slug (equivalents + subsumption stricter / broader): `like:comsvcs_lsass_memory_dump-splunk-sysmon`
`groupby:`	Entity-grouping substring match against `group_by_keys`: `groupby:user`, `groupby:host`
`uses:`	Rules whose predicate tree touches the field (any kind, any value): `uses:CommandLine`
`excludes:`	Rules with top-level `not()` clauses on the field (FP whitelists): `excludes:ParentImage`
`field:` / `value:`	Predicate search; narrows rule cards to those with a matching leaf and drives the indicator tier. Unquoted = substring, wildcards allowed (`value:mimikatz`)
`indicator:`	Shorthand for `field:F value:V`: `indicator:Image=*\powershell.exe`
`kind:`	Filter by predicate kind. Narrows rule cards to those carrying a matching predicate leaf (`vendor:elastic kind:cidr_match`) and drives the indicator tier: `contains` / `starts_with` / `ends_with` / `regex` / `cidr` / `eq` / `in` … (operator aliases `op:`/`match:`)
`has:` / `no:`	`sample`, `field`, `notes`, `refs`, `trace`, `thirdparty`, `rule`, `pattern`, `timewindow`, `threshold`, `newterms`, `sigma`/`elastic`/`splunk`/`kusto`/`chronicle`
`-op:val`	Exclude matches; works on most operators but not `type:`/`like:`/`has:`/`no:` (use `no:<flag>` to exclude a rule flag): `tactic:execution -vendor:splunk`. Standalone `-kind:`/`-field:`/`-value:` drop every rule carrying a matching predicate leaf (`type:rules -kind:is_null`)
`field:"…"` / `value:"…"`	Quoted value = anchored exact match (also allows spaces): `value:"net user"`
`a,b`	Comma = OR inside one operator (`vendor:sigma,elastic`, `severity:high,critical`); repeating a facet merges the same way. `field:`/`value:` never split (literal commas)
`vendors:` / `stage:`	Singular and plural spellings fold to the canonical operator and value: `tactics:` = `tactic:`, `type:event` = `type:events`, `correlation:sequences` = `correlation:sequence`, `has:thresholds` = `has:threshold`
`"quoted phrase"`	Exact-match a multi-word phrase (free text)