Obfuscated IP Download Activity

Status: test
Severity: medium
Log source: product windows, category process_creation
Author: Florian Roth (Nextron Systems), X__Junior (Nextron Systems)
Source: github.com/SigmaHQ/sigma

Detects use of an encoded/obfuscated version of an IP address (hex, octal...) in an URL combined with a download command

MITRE ATT&CK coverage

Tactic	Techniques
Discovery	No specific technique

Event coverage

Provider	Event	Title
Sysmon	Event ID 1	Process creation
Security-Auditing	Event ID 4688	A new process has been created.

Rule body yaml

title: Obfuscated IP Download Activity
id: cb5a2333-56cf-4562-8fcb-22ba1bca728d
status: test
description: Detects use of an encoded/obfuscated version of an IP address (hex, octal...) in an URL combined with a download command
references:
    - https://h.43z.one/ipconverter/
    - https://twitter.com/Yasser_Elsnbary/status/1553804135354564608
    - https://twitter.com/fr0s7_/status/1712780207105404948
author: Florian Roth (Nextron Systems), X__Junior (Nextron Systems)
date: 2022-08-03
modified: 2026-03-16
tags:
    - attack.discovery
logsource:
    category: process_creation
    product: windows
detection:
    selection_command:
        CommandLine|contains:
            - 'Invoke-WebRequest'
            - 'iwr '
            - 'Invoke-RestMethod'
            - 'irm '
            - 'wget '
            - 'curl '
            - 'DownloadFile'
            - 'DownloadString'
    selection_ip_1:
        CommandLine|contains:
            - ' 0x'
            - '//0x'
            - '.0x'
            - '.00x'
    selection_ip_2:
        CommandLine|contains|all:
            - 'http://%'
            - '%2e'
    selection_ip_3:
        # http://81.4.31754
        - CommandLine|re: 'https?://[0-9]{1,3}\.[0-9]{1,3}\.0[0-9]{3,4}'
        # http://81.293898
        - CommandLine|re: 'https?://[0-9]{1,3}\.0[0-9]{3,7}'
        # http://1359248394
        - CommandLine|re: 'https?://0[0-9]{3,11}'
        # http://0121.04.0174.012
        - CommandLine|re: 'https?://(?:0[0-9]{1,11}\.){3}0[0-9]{1,11}'
        # http://012101076012
        - CommandLine|re: 'https?://0[0-9]{1,11}'
        # For octal format
        - CommandLine|re: ' [0-7]{7,13}'
    filter_main_valid_ip:
        CommandLine|re: 'https?://(?:(?:25[0-5]|(?:2[0-4]|1\d|[1-9])?\d)(?:\.|\b)){4}'
    condition: selection_command and 1 of selection_ip_* and not 1 of filter_main_*
falsepositives:
    - Unknown
level: medium

Stages and Predicates

Stage 0: `condition`

selection_command and 1 of selection_ip_* and not 1 of filter_main_*

Stage 1: `selection_command`

selection_command:
    CommandLine|contains:
        - 'Invoke-WebRequest'
        - 'iwr '
        - 'Invoke-RestMethod'
        - 'irm '
        - 'wget '
        - 'curl '
        - 'DownloadFile'
        - 'DownloadString'

Stage 2: `selection_ip_1`

selection_ip_1:
    CommandLine|contains:
        - ' 0x'
        - '//0x'
        - '.0x'
        - '.00x'

Stage 3: `selection_ip_2`

selection_ip_2:
    CommandLine|contains|all:
        - 'http://%'
        - '%2e'

Stage 4: `selection_ip_3`

selection_ip_3:
    - CommandLine|re: 'https?://[0-9]{1,3}\.[0-9]{1,3}\.0[0-9]{3,4}'
    - CommandLine|re: 'https?://[0-9]{1,3}\.0[0-9]{3,7}'
    - CommandLine|re: 'https?://0[0-9]{3,11}'
    - CommandLine|re: 'https?://(?:0[0-9]{1,11}\.){3}0[0-9]{1,11}'
    - CommandLine|re: 'https?://0[0-9]{1,11}'
    - CommandLine|re: ' [0-7]{7,13}'

Stage 5: `not filter_main_valid_ip`

filter_main_valid_ip:
    CommandLine|re: 'https?://(?:(?:25[0-5]|(?:2[0-4]|1\d|[1-9])?\d)(?:\.|\b)){4}'

Exclusions

Top-level NOT(...) conjuncts: predicates this rule actively suppresses.

Field	Kind	Excluded values
`CommandLine`	regex_match	`https?://(?:(?:25[0-5]\|(?:2[0-4]\|1\d\|[1-9])?\d)(?:.\|\b)){4}`

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

Field	Kind	Values
`CommandLine`	match	`0x` corpus 2 (sigma 2) `%2e` corpus 2 (sigma 2) `.00x` corpus 2 (sigma 2) `.0x` corpus 2 (sigma 2) `//0x` corpus 2 (sigma 2) `DownloadFile` corpus 5 (sigma 4, chronicle 1) `DownloadString` corpus 8 (sigma 7, kusto 1) `Invoke-RestMethod` corpus 5 (sigma 5) `Invoke-WebRequest` corpus 13 (sigma 10, elastic 1, chronicle 1, kusto 1) `curl` corpus 12 (sigma 11, chronicle 1) `http://%` corpus 2 (sigma 2) `irm` corpus 5 (sigma 5) `iwr` corpus 13 (sigma 11, chronicle 2) `wget` corpus 8 (sigma 7, chronicle 1)
`CommandLine`	regex_match	`[0-7]{7,13}` corpus 2 (sigma 2) `https?://(?:0[0-9]{1,11}.){3}0[0-9]{1,11}` corpus 2 (sigma 2) `https?://0[0-9]{1,11}` corpus 2 (sigma 2) `https?://0[0-9]{3,11}` corpus 2 (sigma 2) `https?://[0-9]{1,3}.0[0-9]{3,7}` corpus 2 (sigma 2) `https?://[0-9]{1,3}.[0-9]{1,3}.0[0-9]{3,4}` corpus 2 (sigma 2)

`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)

Obfuscated IP Download Activity

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: `condition`

Stage 1: `selection_command`

Stage 2: `selection_ip_1`

Stage 3: `selection_ip_2`

Stage 4: `selection_ip_3`

Stage 5: `not filter_main_valid_ip`

Exclusions

Indicators

Keyboard shortcuts

Search operators

Obfuscated IP Download Activity

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: condition

Stage 1: selection_command

Stage 2: selection_ip_1

Stage 3: selection_ip_2

Stage 4: selection_ip_3

Stage 5: not filter_main_valid_ip

Exclusions

Indicators

Stage 0: `condition`

Stage 1: `selection_command`

Stage 2: `selection_ip_1`

Stage 3: `selection_ip_2`

Stage 4: `selection_ip_3`

Stage 5: `not filter_main_valid_ip`