AS373

AS373 is a legacy autonomous system number registered under ARIN to The MITRE Corporation, a not-for-profit company that operates several U.S. federally funded research and development centers (FFRDCs) from dual headquarters in Bedford, Massachusetts and McLean, Virginia. The registry record is unambiguous — the ARIN RDAP autnum for AS373 lists MITRE (registrant handle THEMIT-1, "The MITRE Corporation") with the ASN handle MITRE-AS-4 — but the routing picture is that of a dormant number. Every routing source consulted agrees AS373 announces zero IPv4 and zero IPv6 prefixes today: RIPEstat shows the AS visible to 0 of 323 RIS peers for v4 and 0 of 322 for v6, CAIDA AS Rank places it at #79459 with an all-zero degree (0 customers, 0 peers, 0 providers) and a singleton customer cone, and no IXP membership resolves. RIPEstat's historical routing status shows AS373 last observed announcing prefixes in 2011 (first_seen 192.190.72.0/24 on 2011-07-22, last_seen 198.136.142.0/24 on 2011-08-06), consistent with a number retained by MITRE but not actively routed since. RPKI posture is not assessable — with no announced prefixes there are no ROAs to validate. No AS373-specific abuse or blocklist signal surfaced as of 2026-07-02 (Spamhaus, BGP Ranking, NANOG-archive spot checks). Note that MITRE the organization publicly disclosed an April 2024 nation-state intrusion into its unclassified NERVE R&D network via Ivanti Connect Secure zero-days; that is an org-level event, not a finding tied to AS373's (unannounced) address space.

Operator

The MITRE Corporation (not-for-profit FFRDC operator; ARIN registrant handle THEMIT-1; ASN handle MITRE-AS-4; Bedford, MA / McLean, VA) [Confirmed] — https://rdap.arin.net/registry/autnum/373, https://www.mitre.org/who-we-are

Country / RIR

US, ARIN [Confirmed] — https://rdap.arin.net/registry/autnum/373

Allocated

1989-07-13 (ARIN RDAP autnum top-level registration event; a first-party RIR registry date, NOT an IEEE/OUI artifact); ASN status active per RDAP [Confirmed] — https://rdap.arin.net/registry/autnum/373

Org status

active not-for-profit corporation (public-interest company operating U.S. government FFRDCs), founded 1958; registrant address Bedford, MA per ARIN [Confirmed] — https://www.mitre.org/who-we-are, https://rdap.arin.net/registry/autnum/373

Security/abuse context (NEUTRAL, DATED)

no AS373-specific abuse/blocklist/hijack signal found as of 2026-07-02 (Spamhaus, BGP Ranking/CIRCL, NANOG archives — absence of evidence, not a certified clean bill). Org-level context: MITRE disclosed an April 2024 nation-state breach of its unclassified NERVE R&D network via Ivanti Connect Secure zero-days (CVE-2023-46805, CVE-2024-21887, first exploited ~2023-12-31); this is an organization-level event, NOT confirmed to AS373's prefixes [Confirmed for the org event; Likely for the abuse-null] — https://www.mitre.org/news-insights/news-release/mitre-response-cyber-attack-one-its-rd-networks, https://www.spamhaus.org/blocklists/, https://github.com/CIRCL/bgp-ranking

Network & routing

Network type

enterprise/institutional research network of a not-for-profit FFRDC operator (not a commercial ISP, transit, or content network); no operator page classifies AS373 itself [Likely] — https://www.mitre.org/who-we-are

Size

dormant — 0 IPv4 prefixes / 0 IPv4 addresses and 0 IPv6 prefixes; CAIDA customer cone = 1 ASN (itself), 0 prefixes, 0 addresses [Confirmed] — https://stat.ripe.net/AS373, https://asrank.caida.org/asns/373

Routing/peering

NOT announced — 0/323 RIS peers see it (v4), 0/322 (v6); CAIDA degree total 0 (customer 0, peer 0, provider 0); RIPEstat observed_neighbours 0; no upstreams or peers observed [Confirmed] — https://stat.ripe.net/AS373#tabId=routing, https://asrank.caida.org/asns/373

Peering policy

none published — no PeeringDB record exists for AS373 (API query returned no result) and no peering-policy page found on mitre.org [Confirmed] — https://www.peeringdb.com/api/net?asn=373

RPKI

not assessable — AS373 announces no prefixes, so there are no ROAs to validate [Unknown] — https://stat.ripe.net/AS373

Historical routing

last observed announcing routes in 2011 (first_seen 192.190.72.0/24 2011-07-22; last_seen 198.136.142.0/24 2011-08-06); no announcements since — legacy/dormant [Confirmed] — https://stat.ripe.net/AS373#tabId=routing

Notable usage

registered to The MITRE Corporation, operator of multiple U.S. government FFRDCs across defense, aviation, healthcare, homeland security, and cybersecurity (e.g. the MITRE ATT&CK framework). No operator page ties public services or traffic to AS373 specifically; this describes the parent org, not verified AS373 traffic

[Likely] — https://www.mitre.org/who-we-are, https://en.wikipedia.org/wiki/Mitre_Corporation

Related ASNs

MITRE also operates other ASNs (e.g. AS5691, MITRE-AS-5) [Likely per third-party context] — https://en.ipshu.com/asn/373

Analyst note

dormant/legacy MITRE ASN. WHOIS resolves to The MITRE Corporation, but AS373 announces nothing and was last seen routing in 2011. Clean/inactive number under a respected research organization.