DNS query for known malicious domain file.io

SIGmediumconfidence 82/100generated 2026-10-18

DNS resolution of a domain tracked by skopnix as blackbyte infrastructure.

ATT&CK: T1071 mitre ↗
Linked actors: blackbyte
False positives: Scoped to one indicator with skopnix confidence 82/100 from 2 independent sources; checked against RFC1918/reserved space, CDN / cloud / scanner ranges and top-site lists (MISP warninglists), GreyNoise when enriched, and skopnix's benign-infrastructure list. Re-validate against last_seen before blocking: infrastructure is re-assigned.

Sigma rule

skopnix-sigma-ioc-domain-file-io-3c5edfac.ymldownload .yml ↓

title: Skopnix - DNS query for known malicious domain file.io
id: bb8307a1-4cef-591f-a787-b8722daca91b
status: experimental
description: DNS resolution of a domain tracked by skopnix as blackbyte infrastructure.
references:
  - https://skopnix.com/ioc/file.io
author: skopnix
date: '2026-10-18'
tags:
  - attack.command-and-control
  - attack.t1071
logsource:
  category: dns
detection:
  selection:
    query: file.io
  condition: selection
falsepositives:
  - Legitimate services sharing the address; verify against skopnix confidence + last_seen
level: medium

How to deploy on Sigma

1.Convert for your SIEM with sigma-cli / pySigma, e.g. sigma convert -t splunk -p sysmon rule.yml.
2.Run it as a hunt first: every rule ships as status experimental.
3.Promote to an alert once a week of results is clean on your data.

Check · The processing pipeline must map the logsource (firewall, dns, proxy, webserver, process_creation) to your field names.

References

skopnix.com/ioc/file.io ↗