AS661

AS661 is a dormant autonomous system registered to the United States Department of Defense (DoD) within the ARIN-managed DNIC-ASBLK-00616-00665 block (AS616–AS665); it announces zero IPv4 and zero IPv6 prefixes today and carries no active BGP peers or upstreams.

ARIN RDAP records a block-level registration event of 1990-04-19, with the autnum record's status still "active" as of the July 2026 data pull (last changed 2025-09-12). AS661 sits inside a 50-ASN block delegated to the DoD Network Information Center (DNIC) rather than being individually numbered on its own, which is standard for legacy DoD ASN grants of this era.

Registrant, technical, and abuse contacts all route to DISA-Columbus (Defense Information Systems Agency) addresses in Whitehall and Columbus, Ohio, with the abuse mailbox disa.columbus.ns.mbx.hostmaster-dod-nic@mail.mil. No public operator website, about page, or peering policy specific to AS661 was found; DISA's general site is the closest public presence, but no source ties it to this ASN by name.

RIPEstat, CAIDA AS Rank, and community-corroboration research independently agree AS661 has never been observed announcing routes: 0 of 325 RIS peers see IPv4, 0 of 320 see IPv6, its CAIDA customer cone is a singleton, and its AS Rank (79,459) sits near the bottom of the ranked universe. RPKI posture cannot be evaluated because there are no announced prefixes to validate.

Exposure

Zero announced prefixes and zero BGP peers mean AS661 currently presents no live routing attack surface; any risk centers on unused/dark address space being squatted by a third party rather than this ASN being actively targeted.

Abuse signal

No abuse, spam, or hijack incident naming AS661 specifically was found in Spamhaus resources, bgp.tools tags, or NANOG archives as of 2026-07-17; the Spamhaus ASN-DROP JSON endpoint returned 404, so that source's coverage is inconclusive rather than confirmed-clean.

Context

Other historically dark DoD IPv4/ASN space has drawn third-party route-squatting since 2021 (documented around AS8003/GRSCORP's consolidation effort), but no source ties that pattern to AS661 individually — treat this as neighborhood context, not a finding about this ASN.

RPKI

Not assessable; no announced prefixes exist to carry ROAs.

Operator

United States Department of Defense (DoD) (ARIN org handle USDDD) [Confirmed] — https://rdap.arin.net/registry/autnum/661

Country / RIR

US, ARIN [Confirmed] — https://rdap.arin.net/registry/autnum/661

Allocated

1990-04-19 (ARIN RDAP autnum TOP-LEVEL registration event for block DNIC-ASBLK-00616-00665); last changed 2025-09-12 [Confirmed] — https://rdap.arin.net/registry/autnum/661

Website / peering policy

Unknown — no public operator website or peering-policy page found specific to AS661 [Unknown] — https://www.disa.mil/

Contacts

NOC/technical/abuse — disa.columbus.ns.mbx.hostmaster-dod-nic@mail.mil; administrative/technical — disa.columbus.ns.mbx.arin-registrations@mail.mil; both DISA-Columbus, 300 North James Road, Whitehall, OH 43213 [Confirmed] — https://rdap.arin.net/registry/autnum/661

Org status

active RIR registration (status: active) but operationally inactive — no routed prefixes observed [Confirmed] — https://rdap.arin.net/registry/autnum/661

IANA reference

none — ASN assignment within an RIR-delegated block, no RFC applies [not applicable, left blank]

Security/abuse context

no public abuse signal found naming AS661 as of 2026-07-17 (Spamhaus ASN-DROP endpoint returned 404, so coverage there is inconclusive, not confirmed-clean)

Network & routing

Network type

U.S. federal government / military ASN; not a commercial ISP or enterprise network [Confirmed] — https://rdap.arin.net/registry/autnum/661

Size / routing

dormant — 0 IPv4 and 0 IPv6 prefixes announced; 0/325 v4 and 0/320 v6 RIS peers see it; customer cone = 1 ASN (itself), 0 prefixes, 0 addresses [Confirmed] — https://stat.ripe.net/AS661, https://asrank.caida.org/asns/661

CAIDA AS Rank

79459; not a clique member; not seen in topology [Confirmed] — https://asrank.caida.org/asns/661

Peering/upstreams

none observed (AS degree total 0: customer 0, peer 0, provider 0) [Confirmed] — https://asrank.caida.org/asns/661

RPKI

not assessable — no announced prefixes, no ROAs to validate [Unknown / not applicable] — https://stat.ripe.net/AS661

Registry block

AS616–AS665 (DNIC-ASBLK-00616-00665); AS661 is one of 50 ASNs in this DoD block, not individually delegated [Confirmed] — https://rdap.arin.net/registry/autnum/661

Analyst note

legacy dormant DoD ASN within a 50-ASN reserved block; no distinguishing individual history found beyond the block-level registration.