Sh4mefulIP Address: 51.161.144.86
Newly observed. IP address 51.161.144.86 is registered to IPv4 address block not managed by the RIPE NCC and geolocates to Canada. It was observed in sh4meful's dataset on July 14, 2026. Over the observation window, it has failed DMARC alignment once, targeting one sender domain. Its reverse DNS resolves to ip86.ip-51-161-144.net. Network context: this address sits within NON-RIPE-NCC-MANAGED-ADDRESS-BLOCK (IPv4 address block not managed by the RIPE NCC), a network sh4meful has observed producing 30 failures across 5 distinct IPs during the same window.
Failure Activity Over Time
Peak activity was observed in the week of July 13, 2026 with 2 failures recorded. Activity in the most recent 30-day window increased sharply compared with the prior period (2 vs 0 failures).
This IP has claimed to send from 1 sender domain monitored by sh4meful. The single targeted domain suggests either a compromised sending source or a spoofing attempt focused on a specific brand.
This page shows DMARC authentication failure data for this IP address. Learn more about this data.
Geolocation Information
- Country:
- CA Canada
- Coordinates:
- 43.6319, -79.3716
WHOIS Information
- Network Name:
- NON-RIPE-NCC-MANAGED-ADDRESS-BLOCK
- CIDR:
51.161.0.0 - 51.162.127.255- Owner:
- IPv4 address block not managed by the RIPE NCC
- Reverse DNS:
-
ip86.ip-51-161-144.net
Last updated: 7/15/2026
Analysis
This IP generated 2 messages that triggered DMARC failures on July 14, 2026, all within a single day. Every message observed from this source failed both SPF and DKIM verification. Receiving mail providers applied a reject disposition, refusing delivery outright.
The reverse DNS record resolves to ip86.ip-51-161-144.net. Whether this represents legitimate mail infrastructure depends on whether the hostname aligns with the domains this address is claiming to send on behalf of.
Geolocation places the host in Canada, on infrastructure operated by IPv4 address block not managed by the RIPE NCC. Abuse-reporting channels in this jurisdiction are generally responsive, and reports to the network operator can result in timely remediation.
The address is registered to IPv4 address block not managed by the RIPE NCC (NON-RIPE-NCC-MANAGED-ADDRESS-BLOCK), an enterprise network operator. Concentrated authentication failures on enterprise address space can indicate either a compromised internal host being used as an unauthorized sending relay, or an organization knowingly or unknowingly operating as a spam source.
Across the wider NON-RIPE-NCC-MANAGED-ADDRESS-BLOCK network, 5 distinct IPs have been associated with 30 authentication failures over 36 observed messages, spanning 3 countries. Most observed IPs on this network contribute to the failure count, suggesting the range as a whole warrants elevated scrutiny.
If your domain appears in the From header of mail from this address, treat it as probable spoofing. Verify that your SPF record does not authorize this host, directly or through nested include mechanisms, and that no DKIM selector you publish has been issued to it. If both checks come back clean, the receiver's reject action is doing its job.
Your DMARC policy posture matters more than any IP-level response here. The enforcement action applied to this mail indicates your policy is already providing protection. Maintaining p=reject across all your domains closes the gap for attackers who manage partial alignment. Domains that remain at p=none long-term tend to be impersonated repeatedly, because the cost to the attacker of attempting is effectively zero.
Blocking this individual address has limited durability: an attacker can rotate to another address in the same /24 subnet at effectively zero cost. More durable responses include monitoring aggregate DMARC reports so new sources are visible as they emerge, tightening SPF to remove overly permissive include chains or +all mechanisms, and ensuring DKIM is signing every legitimate outbound stream so alignment failures are unambiguous. The formal abuse contact for IPv4 address block not managed by the RIPE NCC is listed in ARIN WHOIS records, and timely remediation is achievable through that channel.
External Reputation Lookups
Look up this IP in external threat intelligence and reputation databases (opens in new tab):
Recommended Action
If this IP appears in your own DMARC reports, treat it as an unauthorized sender unless you have specifically verified it as a legitimate service you use. Ensure your DMARC policy is at p=quarantine or p=reject to prevent delivery of messages this IP claims to send from your domain. If you're new to DMARC, our complete guide walks through the mechanics.