I would like to ask if you know of any resources I can reference for ArcSight correlation rules authoring.
In particular, I am looking for Web App and VOIP Security. Thanks in advance.
So first of all, there's an unfortunate shortage of sources on building content for ArcSight. It's part of why I blog about it, because there are only a few people putting information out there. And if SIM's in general are going to mature, then best practices and an open community are part of that maturation. Besides blogs like mine, the ArcSight forums are a good place to get questions answered and share content. Beyond that, I would highly recommend the annual User Conference that ArcSight puts on. For those that can't attend the User Conference, the slides are published to your software site, and definitely worth downloading. And of course ArcSight's own training offerings. But that is pretty much the extent of resources available at the moment.
As far as ways to monitor Web Apps and VoIP Security with ArcSight, it's going to boil down to the log sources you have available. Here are a couple of ideas I have off the top of my head.
For Web App there are tons of optiions. ArcSight works with several web security proxies, IIS and Apache, most IDS/IPS products under the sun, web app servers like Weblogic and WebSphere, and the more popular commercial databases like Oracle, MS-SQL, and DB2. Depending on what's in your web environment and which sources you're drawing from, you have lots of options here. An easy idea might be to create a filter to sift through web server logs for special characters (like < > ' or - ) or requests where the web server returned a 500 or some other obscure error (not 403 or 404).
VoIP is a trickier one to go after since there's no ArcSight connector for CallManager or whatever SIP gateway you use. You could write one with the Flex Connector SDK, but I'm not sure how great your SIP gateway logs are to begin with it comes to security. I think switches, IDS/IPS, and firewall are your best bets here. You'd want to filter firewall logs for packets sourced from your VoIP VLAN address space that might indicate a rogue device connected to your voice network. (Which reminds me, a new version of voiphopper just came out.) You might also want to filter IDS logs for traffic sourced from your VoIP VLANs as well. Hopefully you've already got "switchport port-security maximum 2" set on all of your VoIP ports (and all of your userland switch ports in general) to prevent ARP spoofing/poisoning attacks. In which case, if you send your switch syslogs to ArcSight, a rule to alert on 'NOMAC' messages could be very useful. These can be regular errors, but also occur when someone attempts ARP-based MITM attacks in a port where port-security has been configured.
Anyway, I hope that helps, Anonymous. Good luck with your projects.