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Every day brings a new lesson in cyber threat intelligence (CTI). In this Curated Intel Diary series, we’ll be sharing quick thoughts, tips, and takeaways from the trenches, small insights that make our collective work in CTI just a bit sharper.Here is simple guide to mapping ASNs per sector and region.1) Grab a list of all ASNs by running the following command:curl https://bgp.potaroo.net/cidr/autnums.html > ASNs.txt2) Load this recipe into CyberChef 3) Change Sector in the top regex and Country Code in the lower regexExample Image:4) You could also use this https://urlhaus.abuse.ch/feeds to check what IPs have been tagged as malicious on those ASNs
Analysis Summary
This article focuses on a guide for Cyber Threat Intelligence (CTI) practitioners on researching Autonomous System Numbers (ASNs) and mapping them to sectors and regions, rather than detailing specific malware, tools, or attack techniques.
Therefore, the analysis must reflect the **technique described for CTI research** based on ASNs and associated malicious IPs.
# Tool/Technique: ASN Mapping for CTI Research
## Overview
This describes a methodology for CTI analysts to map Autonomous System Numbers (ASNs) to specific sectors and geographical regions, often used to contextualize threat intelligence or identify potential infrastructure ownership related to malicious activity. It also suggests correlating this mapping with known malicious IPs sourced from resources like URLhaus.
## Technical Details
- Type: Technique (CTI Research Methodology)
- Platform: Command Line Interface (CLI) and Web-based tools (CyberChef, URLhaus feeds)
- Capabilities: Collection of ASN lists, data transformation/filtering via CyberChef, and cross-referencing ASNs with known malicious IPs.
- First Seen: N/A (Described as a "simple guide" in a diary entry from October 2025)
## MITRE ATT&CK Mapping
*(Note: Since this describes a defensive/analytical technique rather than an adversary TTP, direct mapping is difficult. It relates primarily to intelligence gathering.)*
- **TA0008 - Collection**
- T1105 - Ingress Tool Transfer (Indirectly, by locating infrastructure hosting malicious content)
- T1555 - Credentials from Network Sessions (Indirectly, understanding infrastructure context)
## Functionality
### Core Capabilities
- **ASN Data Acquisition:** Retrieving a comprehensive list of ASNs via the Potaroo BGP repository (`curl https://bgp.potaroo.net/cidr/autnums.html`).
- **Data Processing:** Using CyberChef to load the raw data and utilize regular expressions to filter or categorize ASNs based on Sector and Country Code.
- **Malicious IP Correlation:** Checking IPs associated with the identified ASNs against known malicious feeds, specifically referencing the **URLhaus feeds**.
### Advanced Features
- Contextualizing infrastructure based on sector/region metadata derived from BGP data.
## Indicators of Compromise
*None of the artifacts listed are malware or specific threat indicators; they are tools/sources used for intelligence gathering.*
- File Hashes: N/A
- File Names: `ASNs.txt` (Temporary output file)
- Registry Keys: N/A
- Network Indicators: `https://bgp.potaroo.net/cidr/autnums.html` (Data source); `https://urlhaus.abuse.ch/feeds` (Validation source)
- Behavioral Indicators: N/A
## Associated Threat Actors
- Not applicable, as this is an intelligence gathering *procedure*, not an adversary tool.
## Detection Methods
- N/A (This is a methodology used by analysts for detection research, not a detection mechanism itself.)
## Mitigation Strategies
- N/A (This is an analytical technique, not a system vulnerability.)
## Related Tools/Techniques
- IP attribution methods described in other Curated Intelligence articles ("Attribution to IP").
- General CTI data processing tools.