Is this a security problem?
 

When you see an entry in your logs like this:

61.143.54.67 - - [09/May/2002:14:26:20 -0700] "GET /samples/xxx195/thumbs/images/main/images/main/thumbs/thumbs/images/main/images/main/images/main/thumbs/tn_randy_jpg.jpg HTTP/1.0" 404 23767

And it is constantly repeating and lengthening is this someone trying to overload your server? What are they using to do this?

Generally the IP is .cn or .ru

traceroute to 61.143.54.67 (61.143.54.67): 3-30 hops, 38 byte packets
3 192.68.191.146 (192.68.191.146) 0.546 ms (ttl=252!)
4 snv-pos-slac.es.net (134.55.209.1) [AS293 - Energy Sciences Network (ESnet)] 0.772 ms (ttl=251!)
5 paix-pa-snv.es.net (134.55.208.205) [AS293 - Energy Sciences Network (ESnet)] 1.65 ms (ttl=251)
6 fddi2-0-0.core1.paix.teleglobe.net (198.32.176.38) 1.66 ms (ttl=250)
7 if-10-0.core2.PaloAlto.Teleglobe.net (207.45.220.6) [AS6453 - Teleglobe Inc.] 30.5 ms (ttl=245!)
8 if-11-0.core2.Sacramento.Teleglobe.net (64.86.83.206) [AS6453 - Globeinternet - customers] 30.3 ms (ttl=246!)
9 if-6-0.core2.LosAngeles.Teleglobe.net (64.86.83.149) [AS6453 - Globeinternet - customers] 30.6 ms (ttl=247)
10 ix-4-12.core2.LosAngeles.teleglobe.net (64.86.255.6) [AS14080 - AT&T Colombia] 50.2 ms (ttl=246)
11 202.97.48.26 (202.97.48.26) [AS4134 - ChinaNET backbone] 277 ms (ttl=245)
12 p-13-0-r1-c-gdgz-1.cn.net (202.97.33.137) [AS4134 - ChinaNET backbone] 295 ms (ttl=244)
13 61.140.0.2 (61.140.0.2) [AS4134 - CHINAnet] 336 ms (ttl=243)
14 202.105.4.162 (202.105.4.162) [AS4134 - PNAP-SEA] 300 ms (ttl=242)
15 202.105.4.237 (202.105.4.237) [AS4134 - PNAP-SEA] 316 ms (ttl=241)
16 202.105.4.210 (202.105.4.210) [AS4134 - PNAP-SEA] 454 ms (ttl=240)
17 202.96.132.5 (202.96.132.5) [AS4134 - DATA COMMUNICATIONS BUREAU] 420 ms (ttl=239)
18 61.143.63.157 (61.143.63.157) [AS4134 - CHINAnet] 313 ms (ttl=47!)
19 61.143.54.67 (61.143.54.67) [SASUSH - THE EVAL HACKER] 428 ms (ttl=110)

Don't know...but they could be running something like Teleport Pro... on you site......

ban the chinese...