What is malware?

Malware is short for malicious software. It is any code or program that criminals use to harm devices, networks and the people who use them. “Virus” is the word most people reach for, but a virus is only one kind.

What malware is used for

• Stealing information, such as passwords and account details.
• Locking or encrypting your data and demanding payment to release it.
• Installing other unwanted software without your knowledge.
• Taking control of your devices to attack other organisations.

One infection often leads to another. The Australian Signals Directorate (ASD) notes that malware can be the entry point criminals use to reach the rest of your systems and data.

The common kinds

• Viruses insert malicious code into files, and it runs when the file is opened.
• Worms are standalone programs that spread from device to device.
• Trojans look like useful programs and do something harmful when run. Some open a “backdoor” that gives a criminal broad access to the device.
• Info stealers quietly collect logins and other data. Keyloggers record what you type.
• Ransomware encrypts your files and blocks access until a ransom is paid.
• Adware collects information to show targeted advertising. It is rarely dangerous in itself, but it can open pages that carry other malware.

How it gets onto a device

ASD lists four routes.

• A link or attachment in a spam email or message.
• A malicious website that tries to install something when you visit.
• A weakness in software on the device that has not been patched.
• A program you download and install yourself, because it poses as one you trust. Some malware even pretends to be antivirus software.

Signs a device may be infected

• The device is slow, crashes, overheats or loses battery quickly.
• The browser sends you to websites you did not ask for.
• Pop-ups ask you to update or download software.
• Programs or files appear that you do not recognise.
• An account shows logins or changes you did not make.

Any of these can have an innocent cause. Several together are worth a call to whoever looks after your IT.

How to keep it out

The UK’s National Cyber Security Centre says there is no way to protect an organisation completely, so it recommends layers of defence and a plan for when one layer fails.

• Keep devices, applications and operating systems up to date.
• Use antivirus software and let it update automatically.
• Install software only from the maker’s website or an official app store.
• Be wary of links and attachments you were not expecting. See how to spot a phishing email.
• Give staff standard accounts for daily work, so malware that runs has less it can change.
• Keep backups that are separate from the network, as in the 3-2-1 backup rule.

For a fuller list of basics, read A cyber security checklist for small business. Watching devices for the signs above, around the clock, is what our threat detection and monitoring service does.