51.161.65.135📋 Copy

## INTELLIGENCE BRIEFING: IP 51.161.65.135/32

Classification: Moderate Risk | Risk Score: 40/100

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**Executive Summary**

IP address 51.161.65.135 is hosted on OVH infrastructure in Montreal, Quebec, Canada (ASN 16276). The IP resolves to ahostname associated with ahrefs.net (proxy-ca011-san135.ahrefs.net) and exhibits moderate risk characteristics with a risk score of 40. The subnet demonstrates elevated abuse density, indicating this IP shares infrastructure with multiple potentially compromised or misconfigured endpoints.

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**Ownership & Infrastructure**

• Organization: Dmytro, Ahrefs Pte Ltd
• Network: OVH-CUST-281059690
• ASN: 16276 (OVH)
• Registry: ARIN
• CIDR Block: 51.161.65.0/24
• Geolocation: Montreal, Quebec, Canada (CA/QC)
• Infrastructure Type: CloudCompute, Hosting Service
• Network Classification: Cloud-hosted, firewalled with no open services

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**DNS & Resolution**

• PTR Hostname: proxy-ca011-san135.ahrefs.net
• Reverse DNS: Confirmed
• Forward Confirmation: False (reverse only)
• Domain Association: ahrefs.net
• Email Authentication: No SPF, no DMARC records detected

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**Threat & Risk Assessment**

• Risk Score: 40 (Moderate Risk)
• Abuse Confidence: Not assessed
• Known Attacker: No
• Spam Source: No
• Tor Exit Node: No
• Blacklist Count: 0
• DNSBL Listings: 1 of 8 total lists

Control Plane Indicators:

• Operator Score: 0.2174 (Minimal)
• Route Stability: False
• BGP Prefix: 51.161.0.0/17
• DNSSEC: Valid
• DNSBL Listed: Yes

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**Network Neighborhood Analysis**

The /24 subnet (51.161.65.0/24) exhibits concerning abuse characteristics:

• Subnet Classification: High Abuse
• Abuse Density: 0.6094 (60.94%)
• Inherited Risk: 24
• Total Siblings: 256 IPs
• Active Siblings: 207
• Threat Siblings: 156
• Risk Distribution: 0 High, 99 Medium, 1 Low

This IP shares infrastructure with 156 potentially malicious endpoints within the same /24 block.

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**Observation History**

19 observations recorded. Recent signals (June 2026) indicate:

• Blacklist listings with high severity ratings
• Consistent DNS resolution to ahrefs.net domain
• Persistent subnet abuse classification
• Minimal operator score with limited control plane signals

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**Recommended Security Actions**

Firewall Rules:

```bash

# iptables

iptables -A INPUT -s 51.161.65.135 -j DROP

# nftables

nft add rule inet filter input ip saddr 51.161.65.135 drop

# nginx

deny 51.161.65.135;

```

Cloud/WAF Configuration:

• Cloudflare WAF: Block 51.161.65.135 (risk score 40)
• AWS WAF: Block 51.161.65.135/32

Recommendation: Block this IP at perimeter and web application firewalls. The moderate risk score combined with high-abuse subnet classification warrants defensive blocking. Monitor for any legitimate traffic patterns before implementing permanent blocks.

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Report Generated: IPDebrief Intelligence Platform

Data Currency: Real-time analysis

This summary was generated by AI and may contain inaccuracies. Verify critical details independently.