Home > Articles > Security > Network Security

  • Print
  • + Share This
This chapter is from the book

Making the Initial Assessment

Disaster recovery, access rights, and appropriate policies are topics that are often overlooked by those new to security. To keep it simple and easy to remember, the stages of assessing a system’s security can be separated into the “Six Ps”:

  • Patch
  • Ports
  • Protect
  • Policies
  • Probe
  • Physical

The first three are discussed in this section. The fifth — probe — is discussed in the next section, and policies are covered in Chapter 11. You should note that these Six Ps are the invention of this book’s author (just as the numerical grading system was), and are not yet standards in the security industry. They are provided here as a framework for approaching system security.


Patching a system is perhaps the most fundamental part of security. Therefore, when assessing any system’s security, you should check to see whether a procedure is in place to govern the routine updating of all patches. And you should also, of course, check to see that the machines actually have current patches and updates. A written policy is essential, but when performing a security audit, you need to ensure that those policies are actually being followed.

As you are aware, operating system and application vendors occasionally discover security flaws in their products and release patches to correct these flaws. Unfortunately, it is not uncommon to find organizations in which patches have not been applied as late as 30 days or more after their release.

Applying Patches

Applying patches means that the operating system, database management systems, development tools, Internet browsers, and so on are all checked for patches. In a Microsoft environment this should be easy because the Microsoft Web site has a utility that scans your system for any required patches to the browser, operating system, or office products. It is a very basic tenet of security to ensure that all patches are up-to-date. This should be one of your first tasks when assessing a system. Regardless of the operating system or application vendor, you should be able to go to its Web site and find information regarding how to download and install the latest patches.

Once you have ensured that all patches are up-to-date, the next step is to set up a system to ensure that they are kept up-to-date. One simple method is to initiate a periodic patch review where, at a scheduled time, all machines are checked for patches. There are also automated solutions that will patch all systems in your organization. It is imperative that all machines be patched, not just the servers.

Automated Patch Systems

Manually patching machines can be quite cumbersome, and in larger networks, simply impractical. However, there are automated solutions that will patch all systems on your network. These solutions scan your systems at preset times and update any required patches. A few are listed here:

  • Windows Update: For systems running Microsoft Windows, you can set up Windows to automatically patch your system. Recent versions of Windows have this turned on automatically. If your system is older, simply go to www.microsoft.com and click on the link on the left-hand side that says “Update Windows.” This will give that individual machine routing updates for the Windows operating system. This approach does have a few shortcomings, the first being that it will only update Windows and not any other applications on your machine. The second drawback is that it does not provide any way to check patches on a test machine before deploying them to the entire network. Its main advantages are that it is free, and integrated with the Windows operating system.
  • HFNetChkPro: This product is available from http://www.petri.co.il/hfnetchk_pro.htm. It automatically administers and manages patches, including rebooting the patched machines. It is sold on a per seat license, with five seats going for about $200 and 100 seats selling for about $2,100.
  • Zen Works Patch Management: This product is available from Novell at http://www.novell.com/products/zenworks/patchmanagement/. If you are currently using a Novell network, then it might make sense for you to also use their patch management software. There is a licensing fee of about $18 per each device to be patched.
  • Lumenison (formerly known as PatchLink): Available from http://www.lumension.com/ this product also manages and automates the patching process. PatchLink uses an agent-based system. This means an intelligent agent is installed on each workstation to manage patching.
  • McAfee ePolicy Orchestrator: This product (http://www.mcafee.com/us/products/epolicyorchestrator.aspx) is both interesting and popular. It handles the automated patching of your system, and it includes a number of other features. One interesting feature is that it monitors the network for any devices that are connected to the network that are not set up via ePolicy Orchestrator. This prevents “rogue” machines. In larger organizations people setting up their own machines and servers can be a significant security risk. ePolicy Orchestrator also monitors other aspects of your network defense, including antivirus and firewall software.

Other patch management software solutions are available. These four are provided to give you an example of the solutions available and the price range you can expect to pay for them. A simple Internet search using any major search engine should give you several more options you may want to consider.

The choice of patch management system is often affected by other considerations, such as what other software the company uses. For example if you already use McAfee Firewall and antivirus software, then using their patch management system is definitely an option you should seriously consider.

If no automated patch management system is used, then the next best option is scheduled, periodic manual patching. This means that the IT department in that organization has a schedule wherein they routinely scan each machine and update its patches. How frequently this is done is dependent upon the security needs of the organization. Patching quarterly should be considered the absolute minimum for any organization. Monthly is probably appropriate for most businesses. If a higher level of security is desired, then manual patching is probably not the appropriate choice.


As we have discussed in previous chapters, all communication takes place via some port. This is also true for many virus attacks. Frequently virus attacks will utilize some uncommon port to gain access to your system. Recall that ports 1 through 1024 are assigned and used for well-known protocols. We have examined viruses, Trojan horses, and other dangers that operate on specific port numbers. If those ports are closed, then your vulnerability to these specific attacks is significantly reduced.

Unfortunately some system administrators do not make a policy of closing unused ports. This is probably due to the fact that many administrators think that if the firewall is blocking certain traffic, then there is no need to block that port on individual machines. However, this approach provides you with only perimeter security, not layered security. By closing ports on individual machines, you provide a backup in case the firewall is breached. As a rule, any port you do not explicitly need for operations should be closed, and communication should be disallowed on this port. A port is usually associated with a service. For example an FTP service is often associated with ports 21 and 20. In order to close a port on an individual machine, you would need to shut down the service that uses that port. This means those unused services on servers and individual workstations should be shut down.

Both Windows 7 and Linux have built-in port-filtering capability. Windows 2000 Professional also has port-filtering capability whereas Windows XP has a complete firewall solution built into the operating system. This means in addition to shutting down the particular unneeded services on all client machines, you should also shut down the ports. The end of this chapter has exercises that specifically walk you through closing down services on a Windows 7 Machine. This process would be almost identical for Windows 8, Windows Server 2008, or Windows Server 2012.

You should also shut down any unused router ports in your network. If your network is part of a larger wide area network (WAN), then it is likely you have a router connecting you to that WAN. Every open port is a possible avenue of entry for a virus or intruder. Therefore, every port you can close is one less opportunity for such attacks to affect your system. The specifics of how to close a port on a router are particular to the individual router. The documentation that came with your router or the vendor should be able to provide you with specific instructions for how to accomplish this. If you have a vendor servicing your router, then you should make a list of all required ports and request that the vendor close all other ports on the router.


The next phase is to ensure that all reasonable protective software and devices are employed. This means at a minimum having a firewall between your network and the outside world. Firewalls were discussed in Chapters 3 and 4. Clearly more advanced firewalls such as stateful packet inspection firewalls are preferred. When auditing a system, you must note not only whether the system has a firewall, but what type of firewall it has.

You should also consider using an intrusion detection system (IDS) on that firewall and any Web servers. An IDS is considered nonessential by some security experts; you can certainly have a secure network without one.

However, they are the only way to know of impending attacks, and there are free, open source IDS available. For that reason, most experts highly recommend them. The firewall and IDS will provide basic security to your network’s perimeter, but you also need virus scanning. Each and every machine, including servers, must have a virus scanner that is updated regularly. The point has already been made that a virus infection is the greatest threat to most networks. As also previously discussed, it is probably prudent to consider anti-spyware software on all of your systems. This will prevent users of your network from inadvertently running spyware on the network.

Finally, a proxy server, also discussed in Chapter 2, is a very good idea. It not only masks your internal IP addresses, but most proxy servers allow you to discover what Web sites users visit and put on filters for certain sites. Many security experts consider a proxy server to be as essential as a firewall.

In addition to protecting your network, you must also protect data that is transmitted, particularly outside your network. All external connections should be made via a VPN. Having data encrypted prevents hackers from intercepting the data via a packet sniffer. For more secure locations you might even look for all internal transmissions to be encrypted as well.

In short, when assessing the protection of the network, check to see whether the following items are present, properly configured, and functioning:

  • Firewall
  • Antivirus protection
  • Anti-spyware protection
  • IDS
  • Proxy Server or NAT
  • Data transmissions encryption

Be aware that the first two items are met in most networks. Any network that does not have a firewall or antivirus software is so substandard that the audit should probably stop at that point. In fact, it is unlikely that such an organization would even bother to have a security audit. The IDS and data encryption options are probably less common; however, they should be considered for all systems.


In addition to securing your network from unwanted digital access, you must also ensure that it has adequate physical security. The most robustly secure computer that is left sitting unattended in an unlocked room is not at all secure. You must have some policy or procedure governing the locking of rooms with computers as well as the handling of laptops, PDAs, and other mobile computer devices. Servers must be in a locked and secure room with as few people as is reasonably possible having access to them. Backup tapes should be stored in a fireproof safe. Documents and old backup tapes should be destroyed before disposal (e.g., by melting tapes, de-magnetizing hard disks, breaking CDs).

Physical access to routers and hubs should also be tightly controlled. Having the most hi-tech, professional information security on the planet but leaving your server in an unlocked room to which everyone has access is a recipe for disaster. One of the most common mistakes in the arena of physical security is co-locating a router or switch in a janitorial closet. This means that, in addition to your own security personnel and network administrators, the entire cleaning staff has access to your router or switch, and any one of them could leave the door unlocked for an extended period of time.

There are some basic rules you should follow regarding physical security:

  • Server Rooms: The room where servers are kept should be the most fire-resistant room in your building. It should have a strong door with a strong lock, such as a deadbolt. Only those personnel who actually have a need to go in the room should have a key. You might also consider a server room log wherein each person logs in when they enter or exit the room. There are actually electronic locks that record who enters a room, when they enter, and when they leave. Consult local security vendors in your area for more details on price and availability.
  • Workstations: All workstations should have an engraved identifying mark. You should also routinely inventory them. It is usually physically impossible to secure them as well as you secure servers, but you can take a few steps to improve their security.
  • Miscellaneous Equipment: Projectors, CD burners, laptops, and so forth should be kept under lock and key. Any employee that wishes to use one should be required to sign it out, and it should be checked to see that it is in proper working condition and that all parts are present when it is returned.

These measures should be considered by all organizations. Some organizations go much further in ensuring physical security, and we will list some of the more extreme measures here. Most are probably more extreme than businesses require. However if you deal with highly sensitive or classified data, then you might want to consider some or all of these measures.

  • Biometric locks to all server rooms, or equipment storage rooms. Such locks are triggered by a fingerprint scan, and the identity of the person as well as the time they entered the room are recorded.
  • All visitors to the building are logged in (both their entry and exit time) and are escorted by an employee at all times.
  • All bags are inspected when personnel leave, or at least some bags are inspected at random.
  • No portable devices that might record data are allowed on the premises. This includes USB drives, camera phones, or any device that might copy data or record screen images.
  • All printing is logged. Who printed, the time the printing occurred, the document name, and the document size.
  • All copying is logged, similarly to printing.

If you are in a situation that demands a greater than normal security level, these measures may be considered.

  • + Share This
  • 🔖 Save To Your Account