Strange Error Log which caused Apache Server to restart

Question

There are some error logs [Wed May 11 13:27:36 2016] [error] [client 157.55.39.65] (36)File name too long: access to

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failed (filesystem path 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As per the host this has lead to

[Wed May 11 14:04:58 2016] [notice] Graceful restart requested, doing restart

However - thetre is no such file in public_html folder, whose name is that too long and the server failed to open/generate it.

Can anyone help on it pls

Update While checking recent previous logs - the errors are shown for some ip address 157.55.39.152
157.55.39.65
157.55.39.70
157.55.39.224 40.77.167.62 157.55.39.13 157.55.39.21 207.46.13.106

Shocking is that all ip belongs to bingbot. Shall i block bing

Answer 1

Although this particular requesting client resolves to search.msn.com, the Request is of a nature that is often malicious, where the "normal" text is encoded to attempt to evade filtering, pass executable code, etc. If you monitor your web logs, you will often see this type of activity.

You can mitigate against this by dialing down your LimitRequestLine Directive, and similar "Limit" directives to keep these "large" dumps out of your server.

Although, as the documentation suggests, you will likely have to adjust to your situtation, I have without problem used:

LimitRequestLine 512
LimitRequestFields 100
LimitRequestFieldSize 1024
LimitRequestBody 102400

Indeed, this error message looks like a limit (either in config or default) was likely hit. This is what you want to have happen if someone (or, more likely, some bot) attempts to make a Request that exceeds the bounds of any legitimate Request line, etc. on your server.

As to there being "no such file in public_html folder," your web logs will show that MOST of your traffic may be "probing" Requests, where there is in fact no corresponding target on your server.

Finally, as to the restart: it happened long after the "bad" request. I see no evidence that the two are related, and it may have been something as simple as a log rotation or even a manual restart that simply followed the earlier request.

As to "picking" the settings that are right for you, you will (for each directive) have to follow the advice in the documentation. In the case of the LimitRequestLine directive, for example, the documentation notes that:

The LimitRequestLine directive allows the server administrator to set the limit on the allowed size of a client's HTTP request-line. Since the request-line consists of the HTTP method, URI, and protocol version, the LimitRequestLine directive places a restriction on the length of a request-URI allowed for a request on the server. A server needs this value to be large enough to hold any of its resource names, including any information that might be passed in the query part of a GET request.

For additional guidance on these, and MANY, other "security" steps, you might check out the Center for Internet Security (CIS) Security Benchmarks program, which will let you download free guidance for hardening many web servers and operating systems.