AS673

AS673 (DNIC-AS-00673) is a legacy U.S. Army/Department of Defense autonomous system, registered to Headquarters, USAISC, that currently announces zero prefixes in the global BGP routing table. RIPEstat and bgp.tools both confirm 0 of roughly 325 monitored IPv4 peers and 0 of roughly 321 IPv6 peers see it as of mid-July 2026, so its live routing status reads dormant rather than permanently withdrawn.

The ASN has intermittently announced a single IPv4 block, 155.85.164.0/24 (256 addresses), with RIPEstat recording a first-seen date of 2013-04-04 and a last-seen date as recent as 2026-06-05 — meaning it dropped out of the visible table only weeks before this check. No IPv6 space has ever been announced.

ARIN's RDAP autnum record puts the top-level registration (allocation) date at 1990-04-30, independently corroborated by bgp.tools, with a last-changed date of 2011-08-02. The registrant, Headquarters, USAISC (U.S. Army Information Systems Command), lists an address at Fort Huachuca, AZ, while day-to-day abuse and technical contact runs through a DISA-Columbus mailbox in Whitehall, OH.

USAISC itself appears organizationally defunct as a distinct command — Wikipedia records its functions folding into U.S. Army Communications-Electronics Command around October 1996 — but the ARIN registration has not been transferred or renamed since, a common pattern for legacy DoD ASN records. CAIDA ranks AS673 at 67,700 globally with a singleton customer cone and a single inferred peer relationship, no transit provider.

Exposure

One historical /24 (155.85.164.0/24), currently not announced; no IPv6 footprint; consistent with a small administrative/stub military network rather than a public-facing service provider.

Threat signal

SANS Internet Storm Center's AS report lists Threat Level Green with 0 tracked malicious IPs for AS673, and ipapi.is separately classifies it Inactive with 0 currently associated prefixes; no NANOG, Spamhaus, or AbuseIPDB hits were found.

Routing anomaly

bgp.he.net flags AS673 as "announces bogons," but the triggering prefix and basis are undocumented on that page — treat this as an unverified routing-table classification, not a confirmed abuse finding.

RPKI

bgp.he.net reports no valid or invalid RPKI originations recorded for 155.85.164.0/24; a direct RIPEstat rpki-validation check requires a specific prefix and was not run this pass.

Peering

Single observed peer, AS1733 (U.S. Department of Defense), with zero customer downstreams — consistent with a stub military network rather than a transit or commercial ISP.

Operator

Headquarters, USAISC (United States Army Information Systems Command); ARIN org handle HEADQU-3, registrant address Fort Huachuca, AZ [Confirmed] — https://rdap.arin.net/registry/autnum/673

Country / RIR

US, ARIN [Confirmed] — RIPEstat abuse-contact-finder (authoritative_rir: arin)

Allocated

1990-04-30 (ARIN RDAP autnum top-level registration event); last changed 2011-08-02 [Confirmed] — https://rdap.arin.net/registry/autnum/673, corroborated by https://bgp.tools/as/673

Org status

registrant org (USAISC) as a distinct Army command appears organizationally defunct since ~1996 (functions folded into Army CECOM), but the ARIN record itself remains Active and unchanged since 2011 [Likely] — https://en.wikipedia.org/wiki/United_States_Army_Information_Systems_Engineering_Command

Contacts

disa.columbus.ns.mbx.arin-registrations@mail.mil; registrant address NETC-ANC CONUS TNOSC, Fort Huachuca, AZ; tech/abuse contact DISA-Columbus, 300 North James Road, Whitehall, OH 43213 [Confirmed] — https://rdap.arin.net/registry/autnum/673

Security/abuse context (NEUTRAL, DATED)

no notable public abuse signal as of 2026-07-18 — SANS ISC Threat Level Green, 0 tracked malicious IPs; ipapi.is lists it Inactive/0 prefixes; no NANOG/Spamhaus/AbuseIPDB hits found

Network & routing

Network type

U.S. federal government / DoD (Army) stub AS — single-homed leaf network, not transit/commercial [Confirmed] — https://ipinfo.io/AS673

Size

currently 0 announced prefixes (0 IPv4, 0 IPv6); historically announced one /24, 155.85.164.0/24 (256 addresses), last seen 2026-06-05 [Confirmed] — RIPEstat routing-status, https://asrank.caida.org/asns/673

Routing/peering

NOT currently announced — 0/325 v4 and 0/321 v6 RIS peers seeing it; CAIDA degree total 1 (0 customer, 1 peer, 0 provider); sole peer AS1733 (US DoD) per bgp.he.net [Confirmed] — https://bgp.he.net/AS673

RPKI

no valid/invalid RPKI originations recorded for 155.85.164.0/24 per bgp.he.net; RIPEstat rpki-validation not run this pass (requires a prefix parameter) [Likely] — https://bgp.he.net/AS673

Notable usage

sole historical prefix geolocates entirely to the US; IPinfo associates the block with a mail.mil-pattern hostname, consistent with a DoD/Army administrative or mail network [Likely] — https://ipinfo.io/AS673

Related ASN

single observed peer AS1733 (U.S. Department of Defense) [Likely] — https://bgp.he.net/AS673

Analyst note

dormant-but-not-abandoned DoD stub ASN; a 2026-06-05 last-seen date on its sole /24 means it may resume announcing at any time. No website found for the ASN's current operator.