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3 Common Network Security Threats

Whether their ultimate intention is harming your organization or stealing its information, attackers are probably already trying to crack your network. Network engineers need to anticipate these attacks and be ready to mitigate them. Security specialist Sean Wilkins points out three attack methods that most networks will experience.
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Modern technological conveniences can make many parts of our day much easier. But these conveniences come at a cost: The various apps that ease our daily grind also diminish our security. As publicly accessible platforms become more widespread, users are exposed to a constantly expanding array of threats. This article offers a primer about these methods of attack and how they work.

Common Attack Methods

There are many common attack methods, including denial-of-service (DoS) or distributed denial-of-service (DDoS) attacks, social engineering, and malware. This list isn’t exhaustive, but it shows that there are many types of threats, which means that you need many types of protection. (Even if your company’s great big front door has sufficient locks and guards, you still have to protect the back door.)

Some solutions are designed to protect systems from multiple types of attacks, but few solutions can cover all potential attack methods. You need a multilayered security approach, which explains why the “Defense in Depth” method is popular with network security experts. The basic idea behind the Defense in Depth approach is that multiple overlapping protection layers secure a target better than a single all-in-one layer can. A well-designed network security infrastructure has multiple levels of protection, and it includes solutions that are both broad and narrow in their field of view.

Denial-of-Service (DoS/DDoS) Attacks

DoS attacks are among the easiest to understand. They work on the principle of making some device so busy that it can’t perform its job. Any networked device has a certain level of capacity that it’s able to use when connected. The capacity of each device depends on factors such as the processor, the amount of memory, the amount of networking buffers, the processor of the network interface card (if it has one), and the network connection speed.

A successful DoS attack happens when a device’s ability to perform is hindered or prevented. Methods for causing this condition range from simply sending large amounts of traffic at the target device, to triggering the device to fill up its buffers, or triggering the device to enter into an error condition.

A simple DoS attack can be performed by a single third-party networked device focusing all of its available networked capacity onto another networked device with less capacity. Of course, with this method, the target can see where the attack originated and take action, either legally or via some type of countermeasure. The easy solution to this is for the attacker to exploit some other computer to send the traffic; however, the target’s response to the initial attack limits the scope of subsequent attacks to devices with less networked capacity than that of the original attacking device.

An organization like Google has a massive amount of networked capacity, and an attack from a single networked device (regardless of its connection speed or type) won’t put a dent in that capacity. This is where distributed DoS (DDoS) attacks become popular.

With DDoS attacks, instead of using its own device or a single other device to send traffic, the attacker takes control of a group of exploited devices (termed a botnet), which it uses to perform the attack. The path to the attacker is thus indirect, and much harder to trace. Setting up and maintaining a working Botnet requires serious networking skills; less skilled network attackers might not have a means for performing DDoS attacks. Unfortunately, these less skilled attackers can rent existing Botnets set up by their more highly skilled peers. This innovation has made the work of network security professionals very interesting over the last several years.

Social Engineering

One of the most obvious and popular methods of attack has existed for thousands of years. While social engineering isn’t difficult, it requires a certain level of skill to be exceptional. Social engineering doesn’t necessarily require technology; it takes advantage of social methods for extracting information that wouldn’t normally be given directly.

One common example of social engineering that everyone with an email account has likely witnessed is phishing (pronounced like fishing). An attacker sends an email message to a targeted group, with the email disguised to make it appear to be from some trusted source. If users believe that the email is from that trusted source, they’re less likely to worry about giving out their personal information, which can range from usernames and passwords to account numbers and PINs. The attacker can use this extracted information to gain access to some targeted system by simply logging in with the user’s credentials.

There are many styles of social engineering, limited only by the imagination of the attacker. This is why user education in an organization should be a top priority, along with installing network security hardware and software; all of this equipment does little good if an attacker can capture an internal user’s username and password.


The word malware is short for malicious software. In the context of modern network attacks, malware includes attack methods such as viruses, worms, rootkits, spyware, Trojans, spam, and adware. These methods differ in operation but combine in their vision of exploiting some part of a targeted system—including the users. The following list describes each attack method (keep in mind that many of these methods can overlap):

  • Virus. Viruses have long existed in computing. A virus is software programmed to attach to a specific piece of executing code (such as a program file). When that code is run legitimately, the virus is executed and attempts to reproduce itself by spreading to other files.
  • Worm. Worms are one of the most common types of malware. A worm works by attempting to take advantage of some exploit, either in an operating system or in a specific program that runs on top of the operating system. Worms are as dangerous as the programmer wants them to be. Some may just be programmed to spread and do little else; others might spread and then execute some other code that attempts to make the infected device into a Bot for later attacks.
  • Rootkit. The main target of a rootkit is to be invisible. All types of attacks attempt some level of stealth, but rootkits are programmed with stealth as a primary function. If a device is infected, the rootkit can be extremely difficult to remove completely. After infection has occurred, the rootkit may be programmed to do a number of things. One common effect is remotely controlling and executing code on the exploited device.
  • Spyware. Most people have been affected by spyware at some point. Spyware is typically included with publicly available software that has some useful purpose. While the software itself may perform that intended function, it simultaneously performs other actions, such as recording keystrokes or monitoring activity.
  • Trojan. The name comes from the Trojan horse concept; a bit of attacking code hides inside another shell that isn’t considered threatening. The Trojan is just the delivery mechanism; it could spread a virus, worm, or rootkit.
  • Spam. Everyone with an active email address has probably been a victim of spam, the electronic equivalent of junk mail. Spam can come from legitimate sources that are simply trying to advertise their name or product to the public, or it can arrive from other sources that are looking to exploit users. The phishing method discussed previously is commonly delivered by using spam.
  • Adware. Adware is often difficult to distinguish from spyware, because it’s also commonly included with publicly available software. The primary difference between adware and spyware is that adware typically isn’t trying to exploit a machine; it’s merely trying to exploit the user, constantly advertising products or services targeted to that user.

As with social engineering, alert users can be a primary defense against malware attacks.


In this article, I’ve explained three of the most commonly used attack methods on modern networks. Network engineers need a basic level of knowledge about these attack types, how they work, and how to prevent them from succeeding. If you intend to become a network security engineer, this information just scratches the surface of the attack types you’ll need to understand. You’ll also be required to know the attack sub-types, how they’re launched, how they can be mitigated, and the available tools for addressing these attacks.

To obtain this level of knowledge, check out the CCNA/CCNP/CCIE security offerings from Cisco, as well as the offerings from CompTIA and (ISC)2, which develop and manage vendor-neutral security offerings.

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