One Article Review
| Source |  taosecurity |
|---|---|
| Identifiant | 1091766 |
| Date de publication | 2019-04-08 16:56:12 (vue: 2019-04-10 14:01:28) |
| Titre | Troubleshooting NSM Virtualization Problems with Linux and VirtualBox |
| Texte |  I spent a chunk of the day troubleshooting a network security monitoring (NSM) problem. I thought I would share the problem and my investigation in the hopes that it might help others. The specifics are probably less important than the general approach.It began with ja3. You may know ja3 as a set of Zeek scripts developed by the Salesforce engineering team to profile client and server TLS parameters.I was reviewing Zeek logs captured by my Corelight appliance and by one of my lab sensors running Security Onion. I had coverage of the same endpoint in both sensors.I noticed that the SO Zeek logs did not have ja3 hashes in the ssl.log entries. Both sensors did have ja3s hashes. My first thought was that SO was misconfigured somehow to not record ja3 hashes. I quickly dismissed that, because it made no sense. Besides, verifying that intution required me to start troubleshooting near the top of the software stack.I decided to start at the bottom, or close to the bottom. I had a sinking suspicion that, for some reason, Zeek was only seeing traffic sent from remote systems, and not traffic originating from my network. That would account for the creation of ja3s hashes, for traffic sent by remote systems, but not ja3 hashes, as Zeek was not seeing traffic sent by local clients.I was running SO in VirtualBox 6.0.4 on Ubuntu 18.04. I started sniffing TCP network traffic on the SO monitoring interface using Tcpdump. As I feared, it didn't look right. I ran a new capture with filters for ICMP and a remote IP address. On another system I tried pinging the remote IP address. Sure enough, I only saw ICMP echo replies, and no ICMP echoes. Oddly, I also saw doubles and triples of some of the ICMP echo replies. That worried me, because unpredictable behavior like that could indicate some sort of software problem.My next step was to "get under" the VM guest and determine if the VM host could see traffic properly. I ran Tcpdump on the Ubuntu 18.04 host on the monitoring interface and repeated my ICMP tests. It saw everything properly. That meant I did not need to bother checking the switch span port that was feeding traffic to the VirtualBox system.It seemed I had a problem somewhere between the VM host and guest. On the same VM host I was also running an instance of RockNSM. I ran my ICMP tests on the RockNSM VM and, sadly, I got the same one-sided traffic as seen on SO.Now I was worried. If the problem had only been present in SO, then I could fix SO. If the problem is present in both SO and RockNSM, then the problem had to be with VirtualBox -- and I might not be able to fix it.I reviewed my configurations in VirtualBox, ensuring that the "Promiscuous Mode" under the Advanced options was set to "Allow All". At this point I worried that there was a bug in VirtualBox. I did some Google searches and reviewed some forum posts, but I did not see anyone reporting issues with sniffing traffic inside VMs. Still, my use case might have been weird enough to not have been reported.I decided to try a different approach. I wondered if running VirtualBox with elevated privileges might make a difference. I did not want to take ownership of my user VMs, so I decided to install a new VM and run it with elevated privileges.Let me stop here to note that I am breaking one of the rules of troubleshooting. I'm introducing two new variables, when I should |
| Envoyé | Oui |
| Condensat | 2003 2018 after another because bejtlich blogspot both broke but can careful centos change changing checked closer com copyright darned deployments didn don exactly expected fault figure fix fixed granted had have hold hopefully immediately installation introduced issue know linux look many may might moral more need network nic not now nsm options out previous problem problems recently richard rocknsm runs script second see seeing should sides something somewhere story sure take taken taking taosecurity them time traffic tried troubleshooting two variables virtualbox virtualization what when where will workaround www |
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