This is a guest diary by Basil Alawi

One of the challenges that face security administrators is deploying IDS in modern network infrastructure. Unlike hubs, switches doesn't forward every packet to every port in the switch. SPAN port or network TAPS can be used as a workaround in the switched environment.

Fortunately with Vmware ESX/ESXi infrastructure we can configure a group of ports to see all network traffic traversing the virtual switch.

"Promiscuous mode is a security policy which can be defined at the virtual switch or portgroup level in vSphere ESX/ESXi. A virtual machine, Service Console or VMkernel network interface in a portgroup which allows use of promiscuous mode can see all network traffic traversing the virtual switch".

By default promiscuous mode policy is set to reject.

To enable promiscuous mode:

1. Log into the ESXi/ESX host or vCenter Server using the vSphere Client.
2. Select the ESXi/ESX host in the inventory.
3. Click the Configuration tab.
4. In the Hardware section, click Networking.
5. Click Properties of the virtual switch for which you want to enable promiscuous mode.
6. Select the virtual switch or portgroup you wish to modify and click Edit.
7. Click the Security tab.
8. From the Promiscuous Mode dropdown menu, click Accept.

Performance issues:

Using VMXNET 3 vNIC will provide better performance enhancement than other vNIC types.(Figure 1)

Figure 1(VMXNET 3)

Reserving memory and CPU resources is highly recommended to make sure that the resource will be available when it’s needed. (Figure 2)

Figure 2(Reserved Memory)

The test lab setup

The test lab consists of Vmware ESXi , Kali Linux, Security Onion and Metaspoitable. ESXi  5.1 will be the host system and  Kali VM will be the attack server, while Metaspoitable will be  the victim and Security Onion will run the snort instance.(See Figure 3)

Figure 3 (Test Lab)

Test Lab Network Diagram

The Network Configuration

For this experiment the vswicth has been configured with two ports groups. Virtual Machines port group which the default promiscuous mode is set to the default value "Reject" .The second port group is Promiscuous which the promiscuous mode is set to "Accept" ( See Figure 4) 

Figure 4 (Vswitch Configuration)

The Security Onion has been configured with two network interfaces, eth0 for management with IP 192.168.207.12 and eth1 without IP address. eth0 is connect to the "VM Network" port group and eth1 is connected to the "Promiscuous" port group.

Testing Snort:

The first test is scanning the metaspoitable vm with NMAP by running and snort detected this attempted successfully. (Figure 5)

Figure 5 (Snort alerts for Nmap scans)

The second test is trying to brute forcing metaspoitable root password using hydra (Figure 6):

Figure 6  (Hydra brute force alerts)

The third attempt was using metasploit to exploit metaspoitable (See Figure 7).

Figure 7  (metasploit alerts)