Penetration Testing For Dummies. Robert Shimonski
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A HOLISTIC VIEW OF SECURITY
Having an understanding of an organization’s business model and industry will enable you to take a holistic approach to security practices. Gaining that holistic view may require programming, network engineering, and system engineering, as well as understanding endpoints, desktops, storage, and many other systems and services. This doesn’t mean you can’t practice security if you don’t have all these other skills, but it definitely makes a difference on your ability to strategize and lead a security effort, and/or be able to respond to security threats, breaches, and attacks with better efficiency.
Security in a holistic view is also known as defense in depth. Confidentiality, integrity, and availability (CIA) make up a triad and defense in depth and pen testing helps to secure it, which is essentially the entire holistic view of practicing security in an organization.
To be able to conduct a pen test with any amount of confidence, the more you know about security and network architecture, the better. For example, to run a basic pen test, you need to enter a network address or subnet range in your scanning tool.
You need to also know the difference between vulnerability scanning and pen testing and why they’re similar and how they’re different. Figure 1-1 shows the basics of setting up an IP addressing range to scan and identify vulnerabilities. After you know the risks and weaknesses, you can then move into the details on how to exploit (pen test) what has been found so you can learn whether the technology is secured.
FIGURE 1-1: Adding an IP range to scan.
It’s also crucial to understand IP, protocols, networking, and other technologies related (and also not directly related) to security analysis because as weaknesses are identified (perhaps with a scan), then you can then move to exploit them (pen test) no matter what technology you’re presented with (database, mainframes, virtualized systems, for example).
In the following sections, I outline what knowledge you need to be a successful pen tester.
Basic networking
Basic networking includes, but is not limited to, understanding the OSI (open systems interconnect) model. Knowing how data transits from one location (a sender) to another (a receiver) is key to being able to unwind how many attacks occur.
It also includes knowing how routers, switches, hubs, load balancers, firewalls, intrusion prevention devices, and other network black boxes on the wire work. (Black-box security testing refers to testing software security from the outside in. Generally, the tester has little or no knowledge of the internal workings.) If you pen test a router, you need to know how it operates.
The TCP/IP protocol suite also falls under basic networking knowledge. The transmission control protocol (TCP) and Internet protocol (IP) controls how computers connect to the Internet. It includes many of the protocols in the 7-layer OSI model. The Open Systems Interconnection (OSI) model is used as a logical framework to show how data travels from the source to the destination and back to the source through the many technologies that comprise the network, systems, and applications. It’s a model of standards that shows the under the hood actions of the technologies at each layer. Figure 1-2 shows an example of the OSI model.
FIGURE 1-2: Examining the OSI model.
The protocols used in a suite (such as TCP/IP) map to the various layers of the model and perform different functions. For example, FTP operates at a higher layer in the model than TCP or IP. The theory is that, if the lower layers don’t work, then the higher layer protocols won’t operate correctly. The OSI allows you to troubleshoot problems in a workflow manner.
Figure 1-3 shows a wire packet capture that shows a lot of the information you need to read through to conduct a pen test with a tool such as Wireshark. Here you can see packets that when captured can be decoded to tell you the details within them.
Having knowledge of these protocols, how and where they operate, and what is contained in the frames, headers, and other inner details of the packet is what will make you a great pen tester. If you run a pen test and it reports back, for example, that you have a vulnerability in telnet that’s sending packets back and forth in cleartext, you need to determine what path a hacker may take. You can more easily make that determination if you know how the protocols work and what is expected behavior and what can be manipulated versus what could be impacted by a software bug. This way, you can test it yourself first to identify whether you have an issue that might need to be remediated or mitigated.
FIGURE 1-3: Digging into a network packet capture.
General security technology
In the general security technology category are firewalls. Most scans against devices such as a firewall turn up little to no information. Knowing why is helpful to your report. For example, in a ping sweep, you ping the interface and find nothing because the firewall has disabled that protocol that responds.
Figure 1-4 shows a Cisco router firewall log that lists the source and destination IP addresses used to make each connection as well as a description of what that connection did.
Another example is when you run a scan and find open ports are in use on a web server in a DMZ behind a firewall that shouldn’t be. By examining the firewall log that sits in front of these servers, you can see what the source IP address is that’s attempting to make those connections.