Operational resilience

March 3, 2020

In the UK, the National Cyber Security Centre (NCSC) runs an information assurance scheme called Cyber Essentials.  Our blog post series looks at each of the framework’s five focus areas and offers practical hints and tips on security requirements and value to organisations wishing to follow its advice.

This post is the fifth in the Cyber Essentials series, you can read the earlier posts herehere, here and here.  In this post, we look at strategies for protecting yourself from viruses and other kinds of malware.

What is malware?

The term malware is a contraction of malicious software and refers to any kind of software that can damage your computer system. Most hacks require malware to be installed on the victim’s machine, and depending on the motivations of the hacker, the malware could do a variety of different things.

Different categories of malware

Viruses are one category of malware, named so because they attach themselves to other executables (in much the same way biological viruses attach to your body’s cells). Another form of malware is ransomware, which executes on your computer, discovers and encrypts your data and then demands payment. Ransomware is somewhat sophisticated, since hackers generate random encryption keys for each victim. The encryption keys allow bad guys to keep track of their victims and ensure those who pay up can decrypt their data, while those who have not paid cannot access their data (even if they get a key from another victim).

Other kinds of malware you might hear about include worms, Trojans, keyloggers, rootkits, spyware and adware. Bear in mind that not all malware has to install on your computer; some are delivered as scripts that might run inside Microsoft Office documents using the Office Macro language VBA (visual basic for applications). PowerShell and JavaScript are two other kinds of scripting languages that can also be targeted by hackers.

How does malware get onto your computer?

Malware can arrive on your computer system in many ways.


Phishing is the most commonly used threat vector, since criminals can craft believable emails that entice you to click on the malicious attachment or follow the link to a malicious file waiting on the attacker’s website. Phishing doesn’t just happen in email though, so look out for SMS text messages asking you to go to a website, or messages in online forums that entice you to use something specific to the purpose of the forum. Free offers and gift vouchers are often used to entice users to malicious sites, with believable offers like “Fill in our survey to receive a $25 gift voucher” used to hook the victims.

Physical attacks

Physical attacks also work, where you might take receipt of a removable USB storage drive which contains malware. Malicious USB devices are used by hackers specifically targeting your business, so this kind of attack should be taken very seriously. Most malware infections are opportunistic, coming from cybercriminals overseas, but if a USB drop occurs close to where you work or live, the hackers are physically close by. If this occurs, it’s time to call the police and put yourself and your workforce on high alert.

How to defend against malware

There are several countermeasures you can take to defend against malware, some of which are obvious and some of which are less well-known.

Starting with the security control most of you will have heard of, antimalware software can either be a paid-for service, or you can make do with the free Microsoft Windows solution called Defender. If you run Apple Mac computers rather than Windows, MacOS has inbuilt antimalware protections too, including antivirus software. Both Windows and MacOS have additional countermeasures, such as ASLR (address space layout randomisation) and System Integrity Protection, so they are working behind the scenes to keep you safe, making it more difficult for malware to do harm.


Every computer system you have, desktop PCs, laptops and servers, and even systems running in the cloud, should all use these security controls, since every system is a potential target for a cybercriminal. Since most of these controls are built into the operating systems, you need to consider patching your systems as soon as they are available, since a patch might include an updated security control that protects you again new malware variants. The same regime should be adopted for all your smartphones and tablets, since security updates in those are also deployed through software patches.

Application Whitelisting

A less well-known security control called application whitelisting can prevent hackers running harmful code on your computer systems. Application whitelisting requires your IT administrator to create a list of permitted software (the white list) and any other software that tries to execute gets blocked. As a security control, it does add an administrative overhead to running IT systems, but it is incredibly powerful as a malware countermeasure. It’s a simple equation, if the malware isn’t on the list, it doesn’t run, so even zero-day exploits (malware that the antivirus systems don’t know about) won’t run, making it a very robust countermeasure.


The final control we will cover here is that of the sandbox. There are many kinds of sandbox, some running on endpoints (desktops and laptops) and others running on the network, such as on your perimeter firewall. Some applications also include sandboxes, such as web browsers including sandbox protection to execute code in an isolated environment, stopping code from accessing critical operating system functions, thus restricting the harm they cause.

Next steps towards Cyber Essentials compliance

In this post, we looked at key strategies to help protect your business from viruses and other malware, a requirement of the Cyber Essentials scheme.

In our final post of this series, we will look at the fifth baseline technical control and explain how it plays a vital role in determining an organisation’s security posture.

Cyber Essentials Compliance Guide


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