یکی از پرکاربردترین سرویس‌های لینوکس cache اونه که با squid پیاده‌سازی می‌شه.
این squid یه سری log فایل مفید داره که یکی از اونا access.log و در اون فایل‌هایی را که از اینترنت گرفته می‌شن را همراه با IP گیرنده و یه سری کد نشون می‌ده.
مفهوم این کدها را می تونین در ادامه این پست (البته به زبان اصلی ببینید):

Cache Result Codes
TCP_HIT
A valid copy of the requested object was in the cache.

TCP_MEM_HIT
A valid copy of the requested object was in the cache, AND it was in
memory so it did not have to be read from disk.

TCP_NEGATIVE_HIT
The request was for a negatively-cached object. Negative-caching refers
to caching certain types of errors, such as "404 Not Found." The amount
of time these errors are cached is controlled with the negative_ttl
configuration parameter.

TCP_MISS
The requested object was not in the cache.

TCP_REFRESH_HIT
The object was in the cache, but STALE. An If-Modified-Since request was
made and a "304 Not Modified" reply was received.

TCP_REF_FAIL_HIT
The object was in the cache, but STALE. The request to validate the object
failed, so the old (stale) object was returned.

TCP_REFRESH_MISS
The object was in the cache, but STALE. An If-Modified-Since request was
made and the reply contained new content.

TCP_CLIENT_REFRESH
The client issued a request with the "no-cache" pragma.

TCP_IMS_HIT
The client issued an If-Modified-Since request and the object was in the
cache and still fresh.

TCP_IMS_MISS
The client issued an If-Modified-Since request for a stale object.

TCP_SWAPFAIL
The object was believed to be in the cache, but could not be accessed.

TCP_DENIED
Access was denied for this request

UDP_HIT
A valid copy of the requested object was in the cache.

UDP_HIT_OBJ
Same as UDP_HIT, but the object data was small enough to be sent in the UDP
reply packet. Saves the following TCP request.

UDP_MISS
The requested object was not in the cache.

UDP_DENIED
Access was denied for this request.

UDP_INVALID
An invalid request was received.

UDP_RELOADING
The ICP request was "refused" because the cache is busy reloading its metadata.