How to prevent IPs from probing web server ?

Dear Sir/Madam,
    I check my server and receive the logwatch notification as below :

-----------------------------
Connection attempts using mod_proxy:
    220.231.83.199 -> long-name-with-some-inexistent-host:443: 1 Time(s)
    220.231.83.199 -> testphpinvalid.acunetix.com:80: 2 Time(s)

A total of 4 sites probed the server
    123.20.65.244
    220.231.83.199
    221.121.18.170
    222.253.79.154

A total of 2 possible successful probes were detected (the following URLs
contain strings that match one or more of a listing of strings that
indicate a possible exploit):

    /chart?symbol=STB&type=line&width=617&height=377&range=3m&scale=linear&ma_periods_1=0&ma_periods
_2=0&bb_periods=0&bb_deviations=0&symbols=H\xc3\x81&markets=&percentType=true
HTTP Response 200
    /chart?symbol=STB&type=line&width=617&height=377&range=3m&scale=linear&ma_periods_1=0&ma_periods
_2=0&bb_periods=0&bb_deviations=0&symbols=H\xc3\x81T&markets=&percentType=true
HTTP Response 200

Requests with error response codes
    400 Bad Request
       /: 4 Time(s)
       /..%5c..%5c..%5c..%5c..%5c..%5c..%5c..%5c..%5c..%5c/boot.ini: 1 Time(s)
       /images/pins/pinQ.gif: 1 Time(s)
       /ipriceboard/images/flag_en.gif: 1 Time(s)
       /ipriceboard/initAction.do?page=hastc: 1 Time(s)
       /search.do: 1 Time(s)
       /web_scanner_test_file.txt: 1 Time(s)
       /wvs_test_for_inexistent_file.txt: 1 Time(s)
    403 Forbidden
       /: 4 Time(s)
       /TRACE_test: 1 Time(s)
       /TRACK_test: 1 Time(s)
       /css/: 3 Time(s)
       /css/images/: 3 Time(s)
       /css/img/: 2 Time(s)
       /css/img/tabs/: 2 Time(s)
       /css/screener/: 3 Time(s)
       /images/: 3 Time(s)
       /img/: 2 Time(s)
       /js/: 3 Time(s)
       /js/ajax/: 2 Time(s)
       /js/screener/: 3 Time(s)
       /portal/sbsfiles/: 6 Time(s)
       /portal/sbsfiles/ACL/: 3 Time(s)
       /portal/sbsfiles/ACL/others/: 3 Time(s)
       /portal/sbsfiles/ALT/: 3 Time(s)
       /portal/sbsfiles/ALT/others/: 3 Time(s)
       /portal/sbsfiles/ASP/: 3 Time(s)
       /portal/sbsfiles/ASP/others/: 3 Time(s)
       /portal/sbsfiles/ATA/: 3 Time(s)
       /portal/sbsfiles/ATA/others/: 3 Time(s)
       /portal/sbsfiles/BCC/: 2 Time(s)
       /portal/sbsfiles/BCC/others/: 2 Time(s)
       /portal/sbsfiles/BPC/: 2 Time(s)
       /portal/sbsfiles/BPC/others/: 2 Time(s)
       /portal/sbsfiles/BTH/: 2 Time(s)
       /portal/sbsfiles/BTH/others/: 2 Time(s)
       /portal/sbsfiles/BTS/: 3 Time(s)
       /portal/sbsfiles/BTS/others/: 3 Time(s)
       /portal/sbsfiles/BVH/: 3 Time(s)
       /portal/sbsfiles/BVH/others/: 3 Time(s)
       /portal/sbsfiles/BVS/: 3 Time(s)
       /portal/sbsfiles/BVS/others/: 3 Time(s)
       /portal/sbsfiles/CCM/: 3 Time(s)
       /portal/sbsfiles/CCM/others/: 3 Time(s)
       /portal/sbsfiles/CDC/: 2 Time(s)
       /portal/sbsfiles/CDC/others/: 2 Time(s)
       /portal/sbsfiles/CJC/: 3 Time(s)
       /portal/sbsfiles/CJC/others/: 3 Time(s)
       /portal/sbsfiles/CNT/: 3 Time(s)
       /portal/sbsfiles/CNT/others/: 3 Time(s)
       /portal/sbsfiles/CTB/: 2 Time(s)
       /portal/sbsfiles/CTB/others/: 2 Time(s)
--------------------------------------------------------------
 
 As I check day after day, there are a lot of Ips which probed our server and I can't simply deny all by firewall with source Ip . So , please guide me how to prevent these IPs from probing our web server . We use apache tomcat + Linux Cent OS 5.3 + JDK 1.6.0.12 .
 Best regards,
 Hien Huynh