Lucas Zaichkowsky, an enterprise defense architect with CrowdStrike, pointed out that most antimalware tools do a poor job of identifying and blocking botnet threats and offered this advice to help individuals avoid becoming victims:

• Block email attachments containing executable files or ZIP files with executable files like EXE and SCR.
• Install antivirus software. Although not perfect, antivirus software can still catch a large percentage of malware and reduce noise. Free antivirus software such as AVAST!, Microsoft Security Essentials or AVG Free are just as good as commercial offerings, so don’t feel like you have to pay money to get a good product.

Advice from Get Safe Online

• Install internet security software from companies listed on Get Safe Online’s Facebook and Google+ profiles to download a free tool to scan for Gameover Zeus and CryptoLocker, and remove them from your computer
• Do not open attachments in emails unless you are 100% certain that they are authentic
• Make sure your internet security software is up-to-date and switched on at all times
• Make sure your Windows operating system has the latest Microsoft updates applied
• Make sure your software programs have the latest manufacturers’ updates applied
• Make sure all of your files including documents, photos, music and bookmarks are backed up and readily available in case you are no longer able to access them on your computer
• Never store passwords on your computer in case they are accessed by Gameover Zeus or another aggressive malware program

The action related to a strain of malware – meaning malicious software – known as Gameover Zeus.

Malware is typically downloaded by unsuspecting users via what is known as a phishing attack, usually in the form of an email that looks like it comes from somewhere legitimate – such as a bank – when it fact it is designed to trick a person into downloading malicious software.

Once installed on a victim’s machine, Gameover Zeus will search specifically for files containing financial information.

If it cannot find anything it deems of worth, some strains of Gameover Zeus will then install Cryptolocker – a ransomware program that locks a person’s machine until a fee is paid.

The FBI said Gameover Zeus could be responsible for “financial losses in the hundreds of millions of dollars”.