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AbuseIPDB » 51.81.110.21

51.81.110.21 was found in our database!

This IP was reported 57 times. Confidence of Abuse is 0%: ?

ISP	OVH US LLC
Usage Type	Data Center/Web Hosting/Transit
ASN	AS16276
Hostname(s)	proxy-us-east003-cip6.ahrefs.net
Domain Name	ovhcloud.com
Country	🇺🇸 United States of America
City	Warrenton, Virginia

IP info including ISP, Usage Type, and Location provided by IPInfo. Updated weekly.

Important Note: 51.81.110.21 is an IP address from within our whitelist belonging to the subnet 51.81.110.16/28, which we identify as: "Ahrefs Crawler".

Whitelisted netblocks are typically owned by trusted entities, such as Google or Microsoft who may use them for search engine spiders. However, these same entities sometimes also provide cloud servers and mail services which are easily abused. Pay special attention when trusting or distrusting these IPs.

Report 51.81.110.21

Whois 51.81.110.21

IP Abuse Reports for 51.81.110.21:

This IP address has been reported a total of 57 times from 20 distinct sources. 51.81.110.21 was first reported on August 23rd 2026, and the most recent report was 4 hours ago.

Recent Reports: We have received reports of abusive activity from this IP address within the last week. It is potentially still actively engaged in abusive activities.

Reporter	IoA Timestamp (UTC)	Comment	Categories
Anonymous	2026-10-22 06:21:02 (4 hours ago)	apache vulnerability scan	Web App Attack
🇩🇪 palzer.IT	2026-10-22 04:48:15 (6 hours ago)	Report for plesk-apache-badbot: 51.81.110.21 - - [24/Sep/2026:08:21:10 +0200] GET /category-sitemap. ... show more Report for plesk-apache-badbot: 51.81.110.21 - - [24/Sep/2026:08:21:10 +0200] GET /category-sitemap.xml [DOMAIN_REMOVED] 200 6061 - Mozilla/5.0 (compatible; AhrefsBot/7.0; +[DOMAIN_REMOVED] show less	Bad Web Bot
🇮🇩 hermawan	2026-10-20 05:47:44 (2 days ago)	[Tue Oct 20 12:47:43.262684 2026] [security2:error] [pid 201414:tid 139776741070528] [client 51.81.1 ... show more [Tue Oct 20 12:47:43.262684 2026] [security2:error] [pid 201414:tid 139776741070528] [client 51.81.110.21:0] ModSecurity: Access denied with code 403 (phase 1). Matched phrase "AhrefsBot" at REQUEST_HEADERS:user-agent. [file "/etc/modsecurity/coreruleset-4.29.0/rules/REQUEST-913-SCANNER-DETECTION.conf"] [line "166"] [id "913102"] [msg "Found User-Agent associated with web crawler/bot"] [data " Matched Data ARGS charset: - Matched Data TX.1: found within Content-Type multipart form Matched Data: AhrefsBot found within REQUEST_HEADERS:user-agent: mozilla/5.0 (compatible; ahrefsbot/7.0; +http://ahrefs.com/robot/) request_line = GET /index.php/analisis-kondisi-dinamika-atmosfer-laut-dasarian/4220-analisis-kondisi-dinamika-atmosfer-laut-dasarian-tahun-2024/555561542-analisis-dan-prediksi-dasarian-dinamika-atmosfer-laut-dan-prediksi-curah-hujan-pemutakhiran-dasarian-i-november-2024 HTTP/1.1 Reque..."] [severity "CRITICAL"] [ver "OWASP_CRS/3.3.5"] [tag "application-multi"] [tag "language-mu ... show less	Email Spam Hacking
🇮🇩 hermawan	2026-10-20 00:33:21 (2 days ago)	[Tue Oct 20 07:33:20.859035 2026] [security2:error] [pid 1834792:tid 139929061406400] [client 51.81. ... show more [Tue Oct 20 07:33:20.859035 2026] [security2:error] [pid 1834792:tid 139929061406400] [client 51.81.110.21:0] ModSecurity: Access denied with code 403 (phase 1). Matched phrase "AhrefsBot" at REQUEST_HEADERS:user-agent. [file "/etc/modsecurity/coreruleset-4.29.0/rules/REQUEST-913-SCANNER-DETECTION.conf"] [line "166"] [id "913102"] [msg "Found User-Agent associated with web crawler/bot"] [data " Matched Data ARGS charset: - Matched Data TX.1: found within Content-Type multipart form Matched Data: AhrefsBot found within REQUEST_HEADERS:user-agent: mozilla/5.0 (compatible; ahrefsbot/7.0; +http://ahrefs.com/robot/) request_line = GET /index.php/prediksi-iklim/prediksi-musim-tiap-6-bulan-sekali/prediksi-musim-kemarau/prediksi-awal-musim-kemarau/per-kota-kabupaten/555563047-prediksi-6-bulanan-awal-musim-kemarau-tahun-2026-di-kabupaten-situbondo HTTP/1.1 Request URI RAW = /index.php/prediksi-iklim/..."] [severity "CRITICAL"] [ver "OWASP_CRS/3.3.5"] [tag "application-multi"] [tag "language-m ... show less	Email Spam Hacking
🇩🇪 ghostwarriors	2026-10-19 13:20:36 (2 days ago)	Webpage scraping	Brute-Force Bad Web Bot Web App Attack
🇺🇸 TPI-Abuse	2026-10-18 01:06:13 (4 days ago)	(mod_security) mod_security (id:210730) triggered by 51.81.110.21 (proxy-us-east003-cip6.ahrefs.net) ... show more (mod_security) mod_security (id:210730) triggered by 51.81.110.21 (proxy-us-east003-cip6.ahrefs.net): 1 in the last 300 secs; Ports: *; Direction: 1; Trigger: LF_MODSEC; Logs: [Sat Oct 17 21:06:05.575317 2026] [security2:error] [pid 32303:tid 32303] [client 51.81.110.21:55348] ModSecurity: Access denied with code 403 (phase 2). Match of "pmFromFile userdata_wl_extensions" against "TX:extension" required. [file "/etc/apache2/conf.d/modsec_vendor_configs/comodo_apache/10_HTTP_HTTP.conf"] [line "27"] [id "210730"] [rev "5"] [msg "COMODO WAF: URL file extension is restricted by policy\|\|www.phantomkennels.com\|F\|2"] [data ".com"] [severity "CRITICAL"] [tag "CWAF"] [tag "HTTP"] [hostname "www.phantomkennels.com"] [uri "/[email protected]"] [unique_id "atQbfT8qCNjEL6QrGJ4-ngAAAAo"] show less	Brute-Force Bad Web Bot Web App Attack
🇩🇪 palzer.IT	2026-10-15 04:45:32 (1 week ago)	Fail2ban automatic report for plesk-apache-badbot: 51.81.110.21 - - [24/Sep/2026:08:21:10 +0200] GET ... show more Fail2ban automatic report for plesk-apache-badbot: 51.81.110.21 - - [24/Sep/2026:08:21:10 +0200] GET /category-sitemap.xml [DOMAIN_REMOVED] 200 6061 - Mozilla/5.0 (compatible; AhrefsBot/7.0; +[DOMAIN_REMOVED] show less	Bad Web Bot
🇺🇸 TPI-Abuse	2026-10-14 17:30:56 (1 week ago)	(mod_security) mod_security (id:210492) triggered by 51.81.110.21 (proxy-us-east003-cip6.ahrefs.net) ... show more (mod_security) mod_security (id:210492) triggered by 51.81.110.21 (proxy-us-east003-cip6.ahrefs.net): 1 in the last 300 secs; Ports: *; Direction: 1; Trigger: LF_MODSEC; Logs: [Wed Oct 14 13:30:48.098763 2026] [security2:error] [pid 21904:tid 21904] [client 51.81.110.21:36518] ModSecurity: Access denied with code 403 (phase 1). Matched phrase ".htaccess" at REQUEST_URI. [file "/etc/apache2/conf.d/modsec_vendor_configs/comodo_apache/02_Global_Generic.conf"] [line "117"] [id "210492"] [rev "3"] [severity "CRITICAL"] [tag "CWAF"] [tag "Generic"] [hostname "nextngnr.com"] [uri "/Hmklo4.htaccess"] [unique_id "as-8SAIqfx2Z7aLxrbH0xAAAAAY"] show less	Brute-Force Bad Web Bot Web App Attack
🇧🇷 ICS Labs	2026-10-14 15:20:12 (1 week ago)	ICS Labs threat intelligence (ICS Feeds): Brute-Force. Last observed 2026-10-14 UTC.	Brute-Force
🇺🇸 SX Communications	2026-10-14 11:57:04 (1 week ago)	HTTP application-layer DoS / botnet traffic from 51.81.110.21: repeated high-cost dynamic page and f ... show more HTTP application-layer DoS / botnet traffic from 51.81.110.21: repeated high-cost dynamic page and feed requests (profile/tag views, forums, tracker, RSS) at abusive rates via completed TCP/HTTPS. Likely compromised end-user host. show less	DDoS Attack Bad Web Bot Exploited Host
🇺🇸 SX Communications	2026-10-14 05:52:35 (1 week ago)	Blocked abusive HTTP application-layer DoS / botnet traffic from 51.81.110.21: traffic from this add ... show more Blocked abusive HTTP application-layer DoS / botnet traffic from 51.81.110.21: traffic from this address continues high-cost dynamic page and feed requests at abusive rates via TCP/HTTPS despite edge block responses. Likely compromised end-user host. show less	DDoS Attack Bad Web Bot Exploited Host
🇺🇸 johnkarlhill	2026-10-13 20:05:31 (1 week ago)	WebKnight blocked malicious web request on johnkarlhill.com	Brute-Force SSH
🇩🇪 ghostwarriors	2026-10-13 16:50:12 (1 week ago)	Webpage scraping	Brute-Force Bad Web Bot Web App Attack
🇮🇳 dineshskt4all	2026-10-13 13:42:55 (1 week ago)	51.81.110.21 - - [13/Oct/2026:13:42:50 +0000] "GET /wp-sitemap-taxonomies-destination-1.xml HTTP/1.1 ... show more 51.81.110.21 - - [13/Oct/2026:13:42:50 +0000] "GET /wp-sitemap-taxonomies-destination-1.xml HTTP/1.1" 200 805 "-" "Mozilla/5.0 (compatible; AhrefsBot/7.0; +http://ahrefs.com/robot/)" ... show less	IoT Targeted
🇫🇷 GabrielJST	2026-10-13 05:47:52 (1 week ago)	(apache-useragents) Failed apache-useragents trigger with match [redacted] from 51.81.110.21 (US/Uni ... show more (apache-useragents) Failed apache-useragents trigger with match [redacted] from 51.81.110.21 (US/United States/proxy-us-east003-cip6.ahrefs.net) show less	Bad Web Bot

Showing 1 to 15 of 57 reports

Think this IP has been falsely reported? You may request to have the associated reports reviewed and removed. Request Takedown 🚩

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