Suspicious File Download From IP Via Curl.EXE

Status: test
Severity: high
Log source: product windows, category process_creation
Author: Nasreddine Bencherchali (Nextron Systems)
Source: github.com/SigmaHQ/sigma

Detects potentially suspicious file downloads directly from IP addresses using curl.exe

MITRE ATT&CK coverage

Tactic	Techniques
Execution	No specific technique

Event coverage

Provider	Event	Title
Sysmon	Event ID 1	Process creation

Rule body yaml

title: Suspicious File Download From IP Via Curl.EXE
id: 5cb299fc-5fb1-4d07-b989-0644c68b6043
status: test
description: Detects potentially suspicious file downloads directly from IP addresses using curl.exe
references:
    - https://labs.withsecure.com/publications/fin7-target-veeam-servers
    - https://github.com/WithSecureLabs/iocs/blob/344203de742bb7e68bd56618f66d34be95a9f9fc/FIN7VEEAM/iocs.csv
    - https://github.com/pr0xylife/IcedID/blob/8dd1e218460db4f750d955b4c65b2f918a1db906/icedID_09.28.2023.txt
author: Nasreddine Bencherchali (Nextron Systems)
date: 2023-07-27
tags:
    - attack.execution
logsource:
    category: process_creation
    product: windows
detection:
    selection_img:
        - Image|endswith: '\curl.exe'
        - OriginalFileName: 'curl.exe'
    selection_ip:
        CommandLine|re: '://[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}'
    selection_http:
        CommandLine|contains: 'http'
    selection_flag:
        CommandLine|contains:
            - ' -O'  # covers the alias for --remote-name and --output
            - '--remote-name'
            - '--output'
    selection_ext:
        # Note: If you add more extensions please consider adding them also in 9cc85849-3b02-4cb5-b371-3a1ff54f2218
        CommandLine|endswith:
            - '.bat'
            - '.bat"'
            - '.dat'
            - '.dat"'
            - '.dll'
            - '.dll"'
            - '.exe'
            - '.exe"'
            - '.gif'
            - '.gif"'
            - '.hta'
            - '.hta"'
            - '.jpeg'
            - '.jpeg"'
            - '.log'
            - '.log"'
            - '.msi'
            - '.msi"'
            - '.png'
            - '.png"'
            - '.ps1'
            - '.ps1"'
            - '.psm1'
            - '.psm1"'
            - '.vbe'
            - '.vbe"'
            - '.vbs'
            - '.vbs"'
            - ".bat'"
            - ".dat'"
            - ".dll'"
            - ".exe'"
            - ".gif'"
            - ".hta'"
            - ".jpeg'"
            - ".log'"
            - ".msi'"
            - ".png'"
            - ".ps1'"
            - ".psm1'"
            - ".vbe'"
            - ".vbs'"
    condition: all of selection_*
falsepositives:
    - Unknown
level: high
regression_tests_path: regression_data/rules/windows/process_creation/proc_creation_win_curl_download_direct_ip_susp_extensions/info.yml

Stages and Predicates

Stage 0: `condition`

all of selection_*

Stage 1: `selection_img`

selection_img:
    - Image|endswith: '\curl.exe'
    - OriginalFileName: 'curl.exe'

Stage 2: `selection_ip`

selection_ip:
    CommandLine|re: '://[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}'

Stage 3: `selection_http`

selection_http:
    CommandLine|contains: 'http'

Stage 4: `selection_flag`

selection_flag:
    CommandLine|contains:
        - ' -O'
        - '--remote-name'
        - '--output'

Stage 5: `selection_ext`

selection_ext:
    CommandLine|endswith:
        - '.bat'
        - '.bat"'
        - '.dat'
        - '.dat"'
        - '.dll'
        - '.dll"'
        - '.exe'
        - '.exe"'
        - '.gif'
        - '.gif"'
        - '.hta'
        - '.hta"'
        - '.jpeg'
        - '.jpeg"'
        - '.log'
        - '.log"'
        - '.msi'
        - '.msi"'
        - '.png'
        - '.png"'
        - '.ps1'
        - '.ps1"'
        - '.psm1'
        - '.psm1"'
        - '.vbe'
        - '.vbe"'
        - '.vbs'
        - '.vbs"'
        - ".bat'"
        - ".dat'"
        - ".dll'"
        - ".exe'"
        - ".gif'"
        - ".hta'"
        - ".jpeg'"
        - ".log'"
        - ".msi'"
        - ".png'"
        - ".ps1'"
        - ".psm1'"
        - ".vbe'"
        - ".vbs'"

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`	ends_with	`.bat` corpus 4 (sigma 4) `.bat"` corpus 4 (sigma 4) `.bat'` corpus 4 (sigma 4) `.dat` corpus 6 (sigma 6) `.dat"` corpus 4 (sigma 4) `.dat'` corpus 4 (sigma 4) `.dll` corpus 7 (sigma 7) `.dll"` corpus 5 (sigma 5) `.dll'` corpus 5 (sigma 5) `.exe` corpus 6 (sigma 6) `.exe"` corpus 4 (sigma 4) `.exe'` corpus 4 (sigma 4) `.gif` corpus 3 (sigma 3) `.gif"` `.gif'` `.hta` corpus 6 (sigma 6) `.hta"` corpus 4 (sigma 4) `.hta'` corpus 4 (sigma 4) `.jpeg` corpus 3 (sigma 3) `.jpeg"` `.jpeg'` `.log` corpus 2 (sigma 2) `.log"` `.log'` `.msi` corpus 5 (sigma 4, elastic 1) `.msi"` corpus 4 (sigma 4) `.msi'` corpus 4 (sigma 4) `.png` corpus 3 (sigma 3) `.png"` `.png'` `.ps1` corpus 6 (sigma 6) `.ps1"` corpus 4 (sigma 4) `.ps1'` corpus 4 (sigma 4) `.psm1` corpus 5 (sigma 5) `.psm1"` corpus 4 (sigma 4) `.psm1'` corpus 4 (sigma 4) `.vbe` corpus 7 (sigma 7) `.vbe"` corpus 4 (sigma 4) `.vbe'` corpus 4 (sigma 4) `.vbs` corpus 7 (sigma 7) `.vbs"` corpus 4 (sigma 4) `.vbs'` corpus 4 (sigma 4)
`CommandLine`	match	`-O` corpus 7 (sigma 6, chronicle 1) `--output` corpus 4 (sigma 4) `--remote-name` corpus 4 (sigma 4) `http` corpus 39 (sigma 34, elastic 2, chronicle 2, splunk 1)
`CommandLine`	regex_match	`://[0-9]{1,3}.[0-9]{1,3}.[0-9]{1,3}.[0-9]{1,3}` corpus 5 (sigma 5)
`Image`	ends_with	`\curl.exe` corpus 30 (sigma 30)
`OriginalFileName`	eq	`curl.exe` corpus 15 (sigma 12, splunk 3)

`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)

Suspicious File Download From IP Via Curl.EXE

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: `condition`

Stage 1: `selection_img`

Stage 2: `selection_ip`

Stage 3: `selection_http`

Stage 4: `selection_flag`

Stage 5: `selection_ext`

Indicators

Keyboard shortcuts

Search operators

Suspicious File Download From IP Via Curl.EXE

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: condition

Stage 1: selection_img

Stage 2: selection_ip

Stage 3: selection_http

Stage 4: selection_flag

Stage 5: selection_ext

Indicators

Stage 0: `condition`

Stage 1: `selection_img`

Stage 2: `selection_ip`

Stage 3: `selection_http`

Stage 4: `selection_flag`

Stage 5: `selection_ext`