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Apache Access Log Entry: CONNECT Method

Published 25 Oct, 2023 Modified 25 Oct, 2023 Read in 2m 21s Viewed 990 times

Detecting Potential Threats from 'search.51job.com' Connection Attempts


Experience Based


We detected an usual access entry in our apache access logs.

Suspicious Access Log

116.62.12.30 – – [25/Oct/2023:00:07:54 +0000] “CONNECT search.51job.com:443 HTTP/1.0” 404 29489 “-” “-“

This log was found in our apache access log.

The log entry recorded indicates that a client (from IP address 116.62.12.30) tried to use our server as an HTTP proxy to connect to search.51job.com on port 443.

The CONNECT method is a technique used for this purpose, especially for secure connections.

Here’s a breakdown of the log entry:

  • 116.62.12.30: This is the IP address of the client making the request.
  • [25/Oct/2023:00:07:54 +0000]: This is the timestamp of when the request was received.
  • “CONNECT search.51job.com:443 HTTP/1.0”: This indicates that the client tried to use the HTTP CONNECT method to establish a network connection to search.51job.com on port 443 (which is typically used for HTTPS/secure connections).
  • 404: This is the HTTP status code returned by our server. A 404 code means “Not Found,” indicating that our server refused the proxy request. This is a good sign because it means our server is not misconfigured to act as an open proxy.
  • 29489: This is the size of the response in bytes.
  • “-” “- “: These are placeholders for the referrer and user agent, respectively. Both are missing in this request, which is common for automated tools or bots.

What does this mean?

  1. Potential Proxy Probe: The request looks like a probe to see if our server can be used as a proxy. If a server is misconfigured and allows this, it can be exploited by attackers to mask their activities or launch attacks through the victim server.
  2. It Was Blocked: Given that our server responded with a 404 error, it seems like the request was blocked, which is a good sign. It means our server isn’t acting as an open proxy.

What should you do if this happens to you?

Remember, the internet is vast, and automated scanning by bots looking for vulnerabilities is commonplace. The best defense is to be proactive in monitoring and maintaining server security.