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5.3: Windows Security

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    Computer Viruses

    A computer virus, much like a flu virus, is designed to spread from host to host and can replicate itself. In more technical terms, a computer virus is a type of malicious code or program written to alter the way a computer operates and is designed to spread from one computer to another. A virus operates by inserting or attaching itself to a legitimate program or document that supports macros in order to execute its code. In the process, a virus has the potential to cause unexpected or damaging effects, such as harming the system software by corrupting or destroying data (, n.d.).

    How does a computer virus attack?

    Once a virus has successfully attached to a program, file, or document, the virus will lie dormant until circumstances cause the computer or device to execute its code. For a virus to infect your computer, you must run the infected program, which in turn causes the virus code to be executed. This means that a virus can remain dormant on your computer, without showing major signs or symptoms. However, once the virus infects your computer, the virus can infect other computers on the same network. Stealing passwords or data, logging keystrokes, corrupting files, spamming your email contacts, and even taking over your machine are just some of the devastating and irritating things a virus can do. While some viruses can be playful in intent and effect, others can have profound and damaging effects. This includes erasing data or causing permanent damage to your hard disk. Worse yet, some viruses are designed with financial gains in mind. (, n.d.)

    How do computer viruses spread?

    In a constantly connected world, you can contract a computer virus in many ways, some more obvious than others. Viruses can be spread through email and text message attachments, Internet file downloads, and social media scam links. Your mobile devices and smartphones can become infected with mobile viruses through shady App downloads. Viruses can hide disguised as attachments of socially shareable content such as funny images, greeting cards, or audio and video files. To avoid contact with a virus, it’s important to exercise caution when surfing the web, downloading files, and opening links or attachments. To help stay safe, never download text or email attachments that you’re not expecting, or files from websites you don’t trust. (, n.d.)

    What are the signs of a computer virus?

    A computer virus attack can produce a variety of symptoms. Here are some of them: (, n.d.)

    • Frequent pop-up windows. Pop-ups might encourage you to visit unusual sites. Or they might prod you to download antivirus or other software programs.
    • Changes to your homepage. Your usual homepage may change to another website, for instance. Plus, you may be unable to reset it.
    • Mass emails being sent from your email account. A criminal may take control of your account or send emails in your name from another infected computer.
    • Frequent crashes. A virus can inflict major damage on your hard drive. This may cause your device to freeze or crash. It may also prevent your device from coming back on.
    • Unusually slow computer performance. A sudden change in processing speed could signal that your computer has a virus.
    • Unknown programs that startup when you turn on your computer. You may become aware of the unfamiliar program when you start your computer. Or you might notice it by checking your computer’s list of active applications.
    • Unusual activities like password changes. This could prevent you from logging into your computer.

    Computer Malware

    Malware is an abbreviated form of “malicious software.” This is software that is specifically designed to gain access to or damage a computer, usually without the knowledge of the owner. There are various types of malware, including spyware, ransomware, viruses, worms, Trojan horses, adware, or any type of malicious code that infiltrates a computer. Generally, the software is considered malware based on the intent of the creator rather than its actual features. Malware creation is on the rise due to money that can be made through organized Internet crime. Originally malware was created for experiments and pranks, but eventually, it was used for vandalism and destruction of targeted machines. Today, much of malware is created to make a profit from forced advertising (adware), stealing sensitive information (spyware), spreading email spam or child pornography (zombie computers), or extorting money (ransomware). Various factors can make computers more vulnerable to malware attacks, including defects in the operating system (OS) design, all the computers on a network running the same OS, giving users too many permissions, or just because a computer runs on a particular operating system, such as Windows, for example. The best protection from malware — whether ransomware, bots, browser hijackers, or other malicious software — continues to be the usual, preventive advice: be careful about what email attachments you open, be cautious when surfing by staying away from suspicious websites, and install and maintain an updated, quality antivirus program. (, n.d.)

    Vulnerabilities and attacks

    A vulnerability is a system susceptibility or flaw. Many vulnerabilities are documented in the Common Vulnerabilities and Exposures (CVE) database. An exploitable vulnerability is one for which at least one working attack or “exploit” exists.

    To secure a computer system, it is important to understand the attacks that can be made against it, and these threats can typically be classified into one of the categories below:


    A backdoor in a computer system, a cryptosystem, or an algorithm, is any secret method of bypassing normal authentication or security controls. They may exist for a number of reasons, including by original design or poor configuration. They may have been added by an authorized party to allow some legitimate access, or by an attacker for malicious reasons; but regardless of the motives for their existence, they create a vulnerability.

    Denial-of-service attack

    Denial of service attacks are designed to make a machine or network resource unavailable to its intended users. Attackers can deny service to individual victims, such as by deliberately entering a wrong password enough consecutive times to cause the victim account to be locked, or they may overload the capabilities of a machine or network and block all users at once. While a network attack from a single IP address can be blocked by adding a new firewall rule, many forms of Distributed denial of service (DDoS) attacks are possible, where the attack comes from a large number of points – and defending is much more difficult. Such attacks can originate from the zombie computers of a botnet, but a range of other techniques are possible including reflection and amplification attacks, where innocent systems are fooled into sending traffic to the victim.

    Direct-access attacks

    An unauthorized user gaining physical access to a computer is most likely able to directly copy data from it. They may also compromise security by making operating system modifications, installing software worms, keyloggers, covert listening devices, or using wireless mice. Even when the system is protected by standard security measures, these may be able to be bypassed by booting another operating system or tool from a CD-ROM or other bootable media. Disk encryption and Trusted Platform Module are designed to prevent these attacks.


    Eavesdropping is the act of surreptitiously listening to a private conversation, typically between hosts on a network. For instance, programs such as Carnivore and NarusInsight have been used by the FBI and NSA to eavesdrop on the systems of internet service providers. Even machines that operate as a closed system (i.e., with no contact to the outside world) can be eavesdropped upon via monitoring the faint electro-magnetic transmissions generated by the hardware; TEMPEST is a specification by the NSA referring to these attacks.


    Tampering describes a malicious modification of products. So-called “Evil Maid” attacks and security services planting surveillance capability into routers are examples.


    Spoofing, in general, is a fraudulent or malicious practice in which communication is sent from an unknown source disguised as a source known to the receiver. Spoofing is most prevalent in communication mechanisms that lack a high level of security.


    Clickjacking, also known as “UI redress attack” or “User Interface redress attack”, is a malicious technique in which an attacker tricks a user into clicking on a button or link on another webpage while the user intended to click on the top-level page. This is done using multiple transparent or opaque layers. The attacker is basically “hijacking” the clicks meant for the top-level page and routing them to some other irrelevant page, most likely owned by someone else. A similar technique can be used to hijack keystrokes. Carefully drafting a combination of stylesheets, iframes, buttons, and text boxes, a user can be led into believing that they are typing the password or other information on some authentic webpage while it is being channeled into an invisible frame controlled by the attacker.


    One of the most annoying emails to receive is junk email.  This is also referred to as spam, unsolicited bulk email from cyber criminals or unethical companies.  It comes in the form of images and videos.


    Phishing is a cyber-attack that uses disguised email as a weapon. The goal is to trick the email recipient into believing that the message is something they want or need — a request from their bank, for instance, or a note from someone in their company — and to click a link or download an attachment. What really distinguishes phishing is the form the message takes: the attackers masquerade as a trusted entity of some kind, often a real or plausibly real person, or a company the victim might do business with. It's one of the oldest types of cyberattacks, dating back to the 1990s, and it's still one of the most widespread and pernicious, with phishing messages and techniques becoming increasingly sophisticated. (, n.d.)

    While there are several paid-for and free applications that protect against viruses and malware, Windows has built-in applications to monitor the health of your PC and protect it against hostile threats.

    Internet of Things and physical vulnerabilities

    The Internet of Things (IoT) is the network of physical objects such as devices, vehicles, and buildings that are embedded with electronics, software, sensors, and network connectivity that enables them to collect and exchange data – and concerns have been raised that this is being developed without appropriate consideration of the security challenges involved.

    While the IoT creates opportunities for more direct integration of the physical world into computer-based systems, it also provides opportunities for misuse. In particular, as the Internet of Things spreads widely, cyber-attacks are likely to become an increasingly physical (rather than simply virtual) threat. If a front door’s lock is connected to the Internet and can be locked/unlocked from a phone, then a criminal could enter the home at the press of a button from a stolen or hacked phone. People could stand to lose much more than their credit card numbers in a world controlled by IoT-enabled devices. Thieves have also used electronic means to circumvent non-Internet-connected hotel door locks.

    Medical devices have either been successfully attacked or had potentially deadly vulnerabilities demonstrated, including both in-hospital diagnostic equipment and implanted devices including pacemakers and insulin pumps.

    5.3: Windows Security is shared under a not declared license and was authored, remixed, and/or curated by LibreTexts.

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