Malware (malicious software) is a general term for software used to interfere with a computer, gather sensitive information, or gain access to a protected information system. This type of software is created and used by cybercriminals and other malicious actors, even governments, to intentionally harm an information system. 

The most recognizable types of malware are computer viruses , but there are other types such as ransomware , trojans , adware, spyware and worms . Each type of malware has its own way of functioning, so the damage caused by each of them is of different degree. 

Despite the fact that there are certain definitions and divisions of malware, the categories cannot be definitively distinguished, so it often happens that one malware performs activities that are characteristic of other types of malware. 

Malware is distributed in a variety of ways. Most users download malware themselves, but as installed programs and devices communicate on the internet in different ways due to their activity, they sometimes have different vulnerabilities that attackers can take advantage of. In most cases, these vulnerabilities are addressed by software and hardware vendors, so it is important to regularly install software and device updates. 

Malware can perform a variety of operations, ranging from redirecting users to fake websites to destabilising the entire system. A special type of malware are keyloggers, which record keyboard strokes and send the records to third parties. Also, there is a type of malware that has the ability to send several thousand emails from an infected computer. Here are some other common types of malware:

  • A virus is a type of malware that replicates itself in existing files, programs, and even the operating system  itself. It usually modifies the contents of files or deletes them, which can cause the system to crash if a virus deletes a system file;
  • A trojan is a type of malware that, when installed, performs operations that are defined by the attacker, most often deleting or modifying data, but it can often damage the entire system. They usually look like regular and useful installation files, so that is how they got their name;
  • Adware (advertising software) is a type of malware that automatically displays advertisements when searching the internet when it infects the system, which brings revenue to the person who created it;
  • Spyware (spying software) is a type of malware that collects data from an infected system and passes it on to a third party, usually the one which created it. With this malware, unauthorised persons can gain access to passwords  , personal data, correspondence, etc;
  • A worm is a type of malware that replicates itself. This means that if one computer within the system is infected, it is very likely that all computers connected to it will be infected after a certain time. It most often damages the network and the system by slowing down the flow of data in the network. Worms are independent malware, i.e. unlike viruses, they do not have to be linked to an existing program to be transmitted.

Organisations nowadays face one of the biggest security problems and forms of cybercrime, a form of malicious software called ransomware. This form of malware encrypts  files on anything from a single computer all the way up to an entire network, including servers , so that the files cannot be accessed without a decryption key. The attackers then ask for payments in cryptocurrency to provide targets with the decryption key, usually within a short time frame to put more pressure on the targets. 

Some ransomware infections start with clicking on what looks like an innocent attachment that, when opened, downloads the malicious files and begins the encryption process. Larger ransomware campaigns use software exploits and flaws, cracked passwords and other vulnerabilities to gain access to organisational systems using weak points such as internet-facing servers or remote-desktop logins to gain access. The attackers will secretly hunt through the network until they control as much as possible – before encrypting all they can.

Victims of ransomware attack can often be left with few choices; they can either regain access to their encrypted files by paying a ransom to the criminals behind the ransomware, restore files from backups or hope that there is a decryption method freely available.

Small and medium-sized businesses are commonly targeted by ransomware because they tend to have poorer security standards and practices compared to larger corporations.

It is not always easy to recognise malware, as it often happens that users are initially unaware that their device/system is infected. Sometimes malware activity can be noticed due to spontaneous deterioration of system performance. The average user certainly cannot completely remove malware on their own without the use of specific anti-malware software. These programs monitor the system, scan the files downloaded from the internet and email, and if they find any malware, they quarantine it or delete it, depending on the settings. 

However, it is not enough to just install a specific application  that will scan and remove malware - it is also important that users do not install untrusted applications, click on suspicious links, open suspicious emails or visit unreliable websites.

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