Suspicious File Download From IP Via Curl.EXE

Severity: high
Author: Nasreddine Bencherchali (Nextron Systems)
Source: upstream

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

Event coverage

Provider	Event ID	Title
Sysmon	1	Process creation

Stages and Predicates

Stage 1: `all of selection_img`

or:
Image|endswith: '\curl.exe'
OriginalFileName: curl.exe

Stage 2: `all of selection_ip`

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

Stage 3: `all of selection_http`

CommandLine|contains: http

Stage 4: `all of selection_flag`

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

Stage 5: `all of selection_ext`

or:
CommandLine|endswith: .bat
CommandLine|endswith: '.bat'''
CommandLine|endswith: '.bat"'
CommandLine|endswith: .dat
CommandLine|endswith: '.dat'''
CommandLine|endswith: '.dat"'
CommandLine|endswith: .dll
CommandLine|endswith: '.dll'''
CommandLine|endswith: '.dll"'
CommandLine|endswith: .exe
CommandLine|endswith: '.exe'''
CommandLine|endswith: '.exe"'
CommandLine|endswith: .gif
CommandLine|endswith: '.gif'''
CommandLine|endswith: '.gif"'
CommandLine|endswith: .hta
CommandLine|endswith: '.hta'''
CommandLine|endswith: '.hta"'
CommandLine|endswith: .jpeg
CommandLine|endswith: '.jpeg'''
CommandLine|endswith: '.jpeg"'
CommandLine|endswith: .log
CommandLine|endswith: '.log'''
CommandLine|endswith: '.log"'
CommandLine|endswith: .msi
CommandLine|endswith: '.msi'''
CommandLine|endswith: '.msi"'
CommandLine|endswith: .png
CommandLine|endswith: '.png'''
CommandLine|endswith: '.png"'
CommandLine|endswith: .ps1
CommandLine|endswith: '.ps1'''
CommandLine|endswith: '.ps1"'
CommandLine|endswith: .psm1
CommandLine|endswith: '.psm1'''
CommandLine|endswith: '.psm1"'
CommandLine|endswith: .vbe
CommandLine|endswith: '.vbe'''
CommandLine|endswith: '.vbe"'
CommandLine|endswith: .vbs
CommandLine|endswith: '.vbs'''
CommandLine|endswith: '.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 5 (sigma 5) `.bat"` corpus 5 (sigma 5) `.bat'` corpus 5 (sigma 5) `.dat` corpus 7 (sigma 7) `.dat"` corpus 5 (sigma 5) `.dat'` corpus 5 (sigma 5) `.dll` corpus 9 (sigma 9) `.dll"` corpus 6 (sigma 6) `.dll'` corpus 6 (sigma 6) `.exe` corpus 6 (sigma 6) `.exe"` corpus 5 (sigma 5) `.exe'` corpus 5 (sigma 5) `.gif` corpus 4 (sigma 4) `.gif"` corpus 2 (sigma 2) `.gif'` corpus 2 (sigma 2) `.hta` corpus 6 (sigma 6) `.hta"` corpus 5 (sigma 5) `.hta'` corpus 5 (sigma 5) `.jpeg` corpus 4 (sigma 4) `.jpeg"` corpus 2 (sigma 2) `.jpeg'` corpus 2 (sigma 2) `.log` corpus 3 (sigma 3) `.log"` corpus 2 (sigma 2) `.log'` corpus 2 (sigma 2) `.msi` corpus 5 (sigma 5) `.msi"` corpus 5 (sigma 5) `.msi'` corpus 5 (sigma 5) `.png` corpus 4 (sigma 4) `.png"` corpus 2 (sigma 2) `.png'` corpus 2 (sigma 2) `.ps1` corpus 6 (sigma 6) `.ps1"` corpus 5 (sigma 5) `.ps1'` corpus 5 (sigma 5) `.psm1` corpus 6 (sigma 6) `.psm1"` corpus 5 (sigma 5) `.psm1'` corpus 5 (sigma 5) `.vbe` corpus 7 (sigma 7) `.vbe"` corpus 5 (sigma 5) `.vbe'` corpus 5 (sigma 5) `.vbs` corpus 7 (sigma 7) `.vbs"` corpus 5 (sigma 5) `.vbs'` corpus 5 (sigma 5)
`CommandLine`	match	`-O` corpus 3 (sigma 3) `--output` corpus 3 (sigma 3) `--remote-name` corpus 3 (sigma 3) `http` corpus 31 (sigma 31)
`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 19 (sigma 19)
`OriginalFileName`	eq	`curl.exe` corpus 11 (sigma 11)

Neighbors

Equivalent rules

1 other rule has the same matching logic as this one. Useful for cross-vendor comparison or picking the variant your stack supports. See eq_0006.