Today cleverly crafted spear phishing emails and drive-by downloads make it almost trivial for a determined attacker to infect a corporate workstation or laptop. Wombat’s “State of the Phish 2018” report shows that 76% of InfoSec professionals experienced phishing attacks in 2017. Malware Remote Access Toolkits (RATs) like Remcos for Windows can easily be rebuilt with a new name and bound to legitimate applications, documents or presentations. Apple Mac users, myself included, are typically a smug group when it comes to Malware so for them, there’s MacSpy which is nearly as feature rich. A good RAT assumes total control over the workstation or server on which they are installed then it leverages a secure HTTPS connection back to their command and control server. Furthermore, they employ their own proprietary encryption techniques to secure their traffic prior to HTTPS being applied. This prevents commercial outbound web proxies designed to inspect HTTPS traffic from gaining any useful insights into the toolkits nefarious activities. With the existence of sophisticated RATs, we must reconsider our view of the enterprise network. Once a laptop or workstation on the corporate network is compromised in the above fashion all the classic network defenses, firewalls, IDS, and IPS are rendered useless. These toolkits force us to reconsider that the New Network Edge is the server itself, and that requires a new layer in our Defense in Depth model.
The data on our enterprise servers are the jewels that attackers are paid a hefty sum to acquire. Whether it’s a lone hacker for hire by a competitor, a hacktivist group or a rogue nation state, there are bad actors looking to obtain your companies secrets. Normally the ONLY defenses on the corporate network between workstations and servers are the network switches and software firewalls that exist on both ends. The network switches enforce sub-networks (subnets) and virtualized local area networks (VLANs) that impose a logical structure on the physical network. Access Control Lists (ACLs) then define how traffic is routed across these logical boundaries. These ACLs are driven by the needs of the business and meant to reflect how information should flow between different parts of the enterprise. By contrast, the software firewalls on both the workstations and servers also define what is permitted to enter and leave these systems. As defenses, both these methods fall woefully short, but today they’re the last line of defense. We need something far more rigorous that can be centrally managed to defend the New Network Edge, our servers.
As a representation of the businesses processes, switch ACLs are often fairly loose when permitting systems on one network access to those on another. For example, someone on the inside sales team sitting in their cubical on their workstation has access to the Customer Relationship Management (CRM) system which resides on a server that is physically somewhere else. The workstation and server are very likely on different subnets or VLAN within the same enterprise, but ACLs exist that enable the sales person’s workstation access to customer data provided by the CRM system. Furthermore, that CRM system is actually pulling the customer data from a third system, a database server. It is possible that the CRM server and the database server may be on the same physical server, or perhaps in the same server rack, but very possibly on the same logical network. The question is, is there a logical path from the inside sales person’s workstation to the database server, the answer should be no, but guess what? It doesn’t matter. Once the inside salesperson is successfully spear fished then it’s only a matter of time before the attacker has access to the database server through the CRM server.
The attacker will first enable the keylogger, then watch the sales person’s screen to see what they are doing, harvest all their user ids and passwords, perhaps turn on the microphone and listen to their conversations, and inspect all the outgoing network connections. Next, the attacker will use what they’ve harvested and learned to begin their assault, first on the CRM server. Their goal at this point is to establish a secondary beachhead with the greatest potential reach from which to launch their primary assault while keeping the inside sales person’s workstation as their fallback position. From the CRM server, they should be able to easily access many of the generic service machines: DNS, DHCP, NTP, print, file, and database systems. The point here is that where external attackers often have to actively probe a network to see how it responds, internal RAT based attacks can passively watch and enumerate all the ports and addresses typically used. In doing so they avoid any internal dark space honeypots, tripwires, or sweep detectors. So how do we protect the New Network Edge, the server itself?
A new layer needs to be added to our defense in depth model called micro-segmentation or application segmentation. This enforces a strict set of policies on the boundary layer between the server and the network. Cisco, Arista, and other switch providers, with a switch-based view of the world, would have you believe that doing it in the switch is the best idea. VMWare, with its hypervisor view of the world, would have you believe that their new NSX product is the solution. Others like Illumio and Tuffin would have you believe that a server-based agent is the silver bullet for micro-segmentation. Then there’s Solarflare, a NIC company, with its NIC based view of the world, and its new entrant in the market called ServerLock.
Cisco sells a product called Tetration designed to orchestrate all the switches within your enterprise and provide finely grained micro-segmentation of your network traffic. It requires additional Cisco servers be installed to receive traffic flow data from all the switches, processes the data, then provides network admins with both the visibility and orchestration of the security policies across all the switches. There are several downsides to this approach, it is complex, expensive, and can very possibly be limited by the ACL storage capabilities of the top of rack switches. As we scale to 100s of VMs per system or 1,000s of containers these ACLs will likely be stretched beyond their limits.
VMWare NSX includes both an advanced virtual switch and a firewall that both require host CPU cycles to operate. Again, as we scale to 100s of VMs per system the CPU demands placed on the system by both the virtual switch and the NSX firewall will become significant, and measurable. Also, it should be noted that being an entirely software-based solution NSX has a large attackable surface area that could eventually be compromised. Especially given the Meltdown and Spectre vulnerabilities recently reported by Intel. Finally, VMWare NSX is a commercial product with a premium price tag.
This brings us to the agent-based solutions like Illumio and Tuffin. We’ll focus on Illumio which comes with two components the Policy Compute Engine (PCE) and the Virtual Enforcement Node (VEN). The marketing literature states that the VEN is attached to a workload, but it’s an agent installed on every server under Illumio’s control and it reports network traffic flow data into the PCE while also controlling the local OS software firewall. The PCE then provides visualization and a platform for orchestrating security policies. The Achilles heel of the VEN is that it’s a software agent which means that it both consumes x86 CPU cycles and provides a large attackable surface area. Large in the sense that both its agent and the OS-based firewall on which it depends can both be easily circumvented. An attacker need only escalate their privileges to root/admin to hamstring the OS firewall or disable or blind the VEN. Like VMWare NSX, Illumio and Tuffin are premium products.
Finally, we have Solarflare’s NIC based solution called ServerLock. Unlike NSX and Illumio which rely on Intel CPU cycles to handle firewall filtering, Solarflare executes its packet filtering engine entirely within the chip on the NIC. This means that when an inbound network packet is denied access and dropped it takes zero host CPU cycles, compared to the 15K plus x86 cycles required by software firewalls like NSX or IPTables. ServerLock NICs also establish a TLS-based domain of trust with a central ServerLock Manager similar to Illumio’s PCE. The ServerLock Manager receives flow data from all the ServerLock NICs under management and provides Visibility, Alerting and Policy Management. Unlike Illumio though the flow data coming from the ServerLock NICs requires no host CPU cycles to gather and transmit, these tasks are done entirely within the NIC. Furthermore, once the Solarflare NIC is bound to a ServerLock Manager the local control plane for viewing and managing the NIC’s hardware filter table is torn down so even if an application were to obtain root privilege there is no physical path to view or manage the filter table. At this point the, it is only capable of being changed from the specific ServerLock Manager to which it is bound. All of the above comes standard with new Solarflare X2 based NICs that are priced at or below competitive Intel NIC price points. ServerLock itself is enabled as an annual service sold as a site license.
So when you think of micro-segmentation would you rather it be done in hardware or software?
P.S. Someone asked why there is a link to a specific RAT or why I’ve included a link to an article about them, simple it validates that these toolkits are in-fact real, and readily accessible. For some people, threats aren’t real until they can actually see them. Also, another person asked, what if we’re using Salesforce.com, that’s ok, as an attacker instead of hitting the CRM server I’ll try the file servers, intranet websites, print servers, or whatever that inside salesperson has access to. Eventually, if I’m determined and the bounty is high enough, I’ll have access to everything.