[Snort-users] base64 snort options

Joel Esler jesler at ...1935...
Fri Jun 8 15:44:38 EDT 2012


alert tcp $HOME_NET any -> $EXTERNAL_NET $HTTP_PORTS (msg:"Suspicious outbound post"; flow:to_server,established; content:"POST"; http_method; content:"index.php"; http_uri; flowbits:set,badpost; flowbits:noalert; sid:1;)

alert tcp $EXTERNAL_NET $HTTP_PORTS -> $EXTERNAL_NET $HTTP_PORTS (msg:"base64 returned from outbound post"; flow:to_client,established; flowbits:isset,badpost; content:"200"; http_stat_code; content:"text/html"; base64_decode:relative; base64_data;  content:"webmail.vigilante.dk"; sid:2;)

or

alert tcp $EXTERNAL_NET $HTTP_PORTS -> $EXTERNAL_NET $HTTP_PORTS (msg:"base64 returned from outbound post"; flow:to_client,established; flowbits:isset,badpost; content:"200"; http_stat_code; content:"text/html"; base64_decode:relative; base64_data;  content:"varchar("; content:"cast("; distance:0; sid:3;)

Actually the below won't work, the above should.


On Jun 8, 2012, at 3:43 PM, Joel Esler wrote:

> Maybe something like this:
> 
> alert tcp $HOME_NET any -> $EXTERNAL_NET $HTTP_PORTS (msg:"Suspicious outbound post"; flow:to_server,established; content:"POST"; http_method; content:"index.php"; http_uri; flowbits:set,badpost; flowbits:noalert; sid:1;)
> 
> alert tcp $EXTERNAL_NET $HTTP_PORTS -> $EXTERNAL_NET $HTTP_PORTS (msg:"base64 returned from outbound post"; flow:to_client,established; flowbits:isset,badpost; content:"200"; http_stat_code; content:"text/html"; http_header; base64_decode:relative; base64_data;  content:"webmail.vigilante.dk"; sid:2;)
> 
> or
> 
> alert tcp $EXTERNAL_NET $HTTP_PORTS -> $EXTERNAL_NET $HTTP_PORTS (msg:"base64 returned from outbound post"; flow:to_client,established; flowbits:isset,badpost; content:"200"; http_stat_code; content:"text/html"; http_header; base64_decode:relative; base64_data;  content:"varchar("; content:"cast("; distance:0; sid:3;)
> 
> 
> 
> 
> Note, I wrote those off the top of my head.  I didn't test them as I don't have a pcap of the traffic.
> 
> --
> Joel Esler
> Senior Research Engineer, VRT
> OpenSource Community Manager
> Sourcefire
> 
> 
> On Jun 8, 2012, at 2:05 AM, whliudunjun wrote:
> 
>> when i use snort to scan pcap package,the net traffic like following:
>> 
>> the traffic:---------------------------------------------------------------------------------------
>> send:
>> POST /metcon/index.php?id=73EEFFDBC2080030429BE52FA2866576 HTTP/1.1
>> Content-Type: application/x-www-form-urlencoded
>> User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; Axo 9.104.044 )
>> Host: 178.157.202.31
>> Content-Length: 4
>> Cache-Control: no-cache
>> INIT
>> receive:
>> HTTP/1.1 200 OK
>> Date: Wed, 06 Jun 2012 09:58:00 GMT
>> Server: Apache
>> Vary: Accept-Encoding
>> Content-Length: 2196
>> Content-Type: text/html
>> d2VibWFpbC52aWdpbGFudGUuZGs=#ODA=#MDAwMA==#L2luZGV4LnBocD9pZD0xJnR5cGU9YWxsJTI3ZGVjbGFyZSUyMEBzJTIwdmFyY2hhcig0MDAwKTtzZXQlMjBAcz1jYXN0KDB4NjQ2NTYzNkM2MTcyNjUyMDQwNzQyMDc2NjE3MjYzNjg2MTcyMjgzMjM1MzUyOTJDNDA2MzIwNzY2MTcyNjM2ODYxNzIyODMyMzUzNTI5MjA2NDY1NjM2QzYxNzI2NTIwNzQ2MTYyNkM2NTVGNjM3NTcyNzM2RjcyMjA2Mzc1NzI3MzZGNzIyMDY2NkY3MjIwNzM2NTZDNjU2Mzc0MjA2MTJFNkU2MTZENjUyQzYyMkU2RTYxNkQ2NTIwNjY3MjZGNkQyMDczNzk3MzZGNjI2QTY1NjM3NDczMjA2MTJDNzM3OTczNjM2RjZDNzU2RDZFNzMyMDYyMjA3NzY4NjU3MjY1MjA2MTJFNjk2NDNENjIyRTY5NjQyMDYxNkU2NDIwNjEyRTc4NzQ3OTcwNjUzRDI3NzUyNzIwNjE2RTY0MjAyODYyMkU3ODc0Nzk3MDY1M0QzOTM5MjA2RjcyMjA2MjJFNzg3NDc5NzA2NTNEMzMzNTIwNkY3MjIwNjIyRTc4NzQ3OTcwNjUzRDMyMzMzMTIwNkY3MjIwNjIyRTc4NzQ3OTcwNjUzRDMxMzYzNzI5MjA2RjcwNjU2RTIwNzQ2MTYyNkM2NTVGNjM3NTcyNzM2RjcyMjA2NjY1NzQ2MzY4MjA2RTY1Nzg3NDIwNjY3MjZGNkQyMDc0NjE2MjZDNjU1RjYzNzU3MjczNkY3MjIwNjk2RTc0NkYyMDQwNzQyQzQwNjMyMDc3Njg2OTZDNjUyODQwNDA2NjY1NzQ2MzY4NUY3Mzc0NjE3NDc1NzMzRDMwMjkyMDYyNjU2NzY5NkUyMDY1Nzg2NTYzMjgyNzc1NzA2NDYxNzQ2NTIwNUIyNzJCNDA3NDJCMjc1RDIwNzM2NTc0MjA1QjI3MkI0MDYzMkIyNzVEM0Q3Mjc0NzI2OTZEMjg2MzZGNkU3NjY1NzI3NDI4NzY2MTcyNjM2ODYxNzIyODM0MzAzMDMwMjkyQzVCMjcyQjQwNjMyQjI3NUQyOTI5MkI2MzYxNzM3NDI4MzA3ODMzNjMzNjM5MzYzNjM3MzIzNjMxMzY2NDM2MzUzMjMwMzczMzM3MzIzNjMzMzM2NDMyMzIzNjM4MzczNDM3MzQzNzMwMzM2MTMyNjYzMjY2MzY2NTM2MzEzNjM0MzY2MTM2NjMzNzMwMzY2NjM2MzkzNzMxMzczNzM2MzUzNjM0MzI2NTM3MzUzNjMxMzI2NjM2NjEzNzMzMzI2NTM3MzAzNjM4MzczMDMzNjYzNzMzMzYzOTM2MzQzMzY0MzMzMjMyMzIzMjMwMzczNzM2MzkzNjM0MzczNDM2MzgzMzY0MzIzMjMzMzAzMjMyMzIzMDM2MzgzNjM1MzYzOTM2MzczNjM4MzczNDMzNjQzMjMyMzMzMDMyMzIzMjMwMzczMzM3MzQzNzM5MzY2MzM2MzUzMzY0MzIzMjM2MzQzNjM5MzczMzM3MzAzNjYzMzYzMTM3MzkzMzYxMzY2NTM2NjYzNjY1MzYzNTMyMzIzMzY1MzM2MzMyNjYzNjM5MzYzNjM3MzIzNjMxMzY2NDM2MzUzMzY1MjA2MTczMjA3NjYxNzI2MzY4NjE3MjI4MzEzMDM2MjkyOTI3MjkyMDY2NjU3NDYzNjgyMDZFNjU3ODc0MjA2NjcyNkY2RDIwNzQ2MTYyNkM2NTVGNjM3NTcyNzM2RjcyMjA2OTZFNzQ2RjIwNDA3NDJDNDA2MzIwNjU2RTY0MjA2MzZDNkY3MzY1MjA3NDYxNjI2QzY1NUY2Mzc1NzI3MzZGNzIyMDY0NjU2MTZDNkM2RjYzNjE3NDY1MjA3NDYxNjI2QzY1NUY2Mzc1NzI3MzZGNzIyMCUyMGFzJTIwdmFyY2hhcig0MDAwKSk7ZXhlYyhAcyk7LS0=#X19fXw==#TW96aWxsYS81LjAgKFdpbmRvd3MgTlQgNS4xKSBBcHBsZVdlYktpdC81MzUuMTkgKEtIVE1MLCBsaWtlIEdlY2tvKSBDaHJvbWUvMTguMC4xMDI1LjE2MiBTYWZhcmkvNTM1LjE5##fDgxMw==#
>> 
>> end-------------------------------------------------------------------------------------------------------------------------------------------------------
>> 
>> base64:
>> d2VibWFpbC52aWdpbGFudGUuZGs=#
>> ascii:webmail.vigilante.dk
>> 
>> the receive data is encode using base64,so i write a snort rules to detected it:
>> 41 alert tcp $EXTERNAL_NET $HTTP_PORTS -> $HOME_NET any (msg:"Trojan SQL injection code receive"; flow:to_client,established;content:"HTTP/1.1 200 OK";content:"webmail.vigilante.dk";clas    stype:trojan-activity; sid:10000043; rev:1;)
>> 
>> why this sig can't detect above traffic,is there anyone can tell me why?or i write rules at a wrong way,or i need to open some config option.
>> 
>> 
>> 
>> 
>> 
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