mod_security blocks only internet explorer

Question

I installed mod_security with an apache server, and now it's blocking only ie7/8/9 browser. (I can browse the web with firefox/chromium/etc)

The logs say:

Message: String match within "Proxy-Connection Lock-Token Content-Range Translate via if" at REQUEST_HEADERS_NAMES:Connection. [file "/etc/apache2/mod_security/modsecurity_crs_30_http_policy.conf"] [line "99"] [id "960038"] [msg "HTTP header is restricted by policy"] [data "Connection"] [severity "WARNING"] [tag "POLICY/HEADER_RESTRICTED"] [tag "POLICY/FILES_NOT_ALLOWED"] [tag "WASCTC/WASC-21"] [tag "OWASP_TOP_10/A7"] [tag "PCI/12.1"] [tag "WASCTC/WASC-15"] [tag "OWASP_TOP_10/A7"] [tag "PCI/12.1"]
Message: Access denied with code 403 (phase 2). [file "/etc/apache2/mod_security/modsecurity_crs_49_enforcement.conf"] [line "25"] [msg "Anomaly Score Exceeded (score 20): Common SPAM/Email Harvester crawler"]
Action: Intercepted (phase 2)
Stopwatch: 1337888078594451 2694 (918 2353 -)
Producer: ModSecurity for Apache/2.5.12 (http://www.modsecurity.org/); core ruleset/2.0.6.
Server: Apache

And the rule id "960038" is:

SecRule REQUEST_HEADERS_NAMES "@within %{tx.restricted_headers}""phase:2,t:none,pass,nolog,auditlog,msg:'HTTP header is restricted by policy',id:'960038',tag:'POLICY/HEADER_RESTRICTED',tag:'POLICY/FILES_NOT_ALLOWED',tag:'WASCTC/WASC-21',tag:'OWASP_TOP_10/A7',tag:'PCI/12.1',tag:'WASCTC/WASC-15',tag:'OWASP_TOP_10/A7',tag:'PCI/12.1',severity:'4',logdata:'%{matched_var}',setvar:'tx.msg=%{rule.msg}',setvar:tx.anomaly_score=+%{tx.warning_anomaly_score},setvar:tx.policy_score=+%{tx.warning_anomaly_score},setvar:tx.%{rule.id}-POLICY/HEADERS_RESTRICTED-%{matched_var_name}=%{matched_var}"

I have one main question and two other derived from the first:

• How do I know what this rule makes?
  • Is it safe to ignore this rule?
  • Is there any way to modify the rule in order to allow ie to navigate the web?

Answer 1

1. Answering Your First Question Mod-Security provide us a very detailed documentation about the syntax of its Rule Language and following is the link to its documentation. ModSecurity Rule Language

2. TX is for user defined variable tx.restricted_headers it defines your HTTP policy like

   SecAction "phase:1,t:none,nolog,pass,setvar:'tx.restricted_headers=/Proxy-Connection/ /Lock-Token/ /Content-Range/ /Translate/ /via/ /if/'" for more detailed information refer this HTTP Policy

3. The Rule you have mentioned above is not blocking but it is incrementing a numerial value maintained against suspicious header name as mentioned in the HTTP policy i explained above.

4. The Rule that is blocking IE as seen from the logs mentioned

   Message: Access denied with code 403 (phase 2). [file "/etc/apache2/mod_security/modsecurity_crs_49_enforcement.conf"] [line "25"] [msg "Anomaly Score Exceeded (score 20): Common SPAM/Email Harvester crawler"]

You can modify the anomaly score threshold or can change your HTTP policy.The Rule you have mentioned is correct and don't need to be commented.I hope you get my point