A computer virus is a program or piece of code that tends to be malicious and is loaded onto your computer without your knowledge and runs against your wishes.

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139
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What should you do if you catch ransomware mid-operation?

You boot up your computer one day and while using it you notice that your drive is unusually busy. You check the System Monitor and notice that an unknown process is using the CPU and both reading and ...
133
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5answers
16k views

How can USB sticks be dangerous?

We all know the story of the USB drive left outside a power plant which was found by a worker and inserted into a computer to see the contents which then allowed a hack to ensue. Here is my question, ...
129
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11answers
16k views

Can a computer virus be stored somewhere else than on the hard drive?

Are there viruses that have managed to hide themselves somewhere other than on the hard drive? Like CPU cache or on the motherboard? Is it even possible? Say I get a virus, so I get rid of the HDD ...
88
votes
2answers
18k views

Can a rogue .wmv file “hijack” Windows Media Player?

I've downloaded a .wmv file using P2P. Attempting to play it with Media Player Classic (K-Lite Codec Pack) only gave me a green square in the playback window: I noticed that the video came with a ...
81
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4answers
7k views

What is the risk of copy and pasting Linux commands from a website? How can some commands be invisible? [duplicate]

Like all beginners in the land of Linux, I usually look for websites that contain some useful shell commands, mark it with my mouse, copy it (CTRL + C) and paste it into a terminal. For example, if ...
67
votes
6answers
38k views

Should I get an antivirus for Ubuntu?

Considering the recent thread regarding anti-virus for the Mac I wonder how many of the arguments put forth are relevant today to Linux systems, specifically Ubuntu. There are no known Ubuntu ...
61
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5answers
18k views

Can my mouse have virus and infect other machines?

This is my mouse. I used it with my old computer which was full of viruses. If I use this mouse for my new PC, can my new computer be infected from my mouse?
51
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10answers
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Can headphones transmit malware?

Can headphones transmit malware? My friend borrowed my headphones (a pair of Apple EarPods) and plugged them into his Android mobile phone for a few minutes in order to listen to a voice message. ...
50
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8answers
13k views

Should I get an antivirus for my Mac?

There are some people saying that people should use an antivirus software on Mac. And there are thousands of people claiming that Macs don't get viruses (under this term I mean spyware / malware as ...
49
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6answers
10k views

Virus Encoded in Video

So I'm not familiar at all with IT Security, but I'm a bit curious about something. I was watching a TV show and at one point, a virus spreads through an office. They investigate and find out that the ...
38
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7answers
10k views

Can cookies carry viruses?

I was wondering whether a cookie can carry a virus (or any security-threatening code). In some sense it is similar to a download. So by simply visiting a site, could I get harmed?
37
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7answers
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Does a virus need to be clicked on to function?

Can a virus infect my Windows XP operating system by its mere presence? I mean, if I copy/paste a virus on my computer and I never click on it, will it infect my computer or will it remain dormant, ...
37
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5answers
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Can malicious code trigger without the user executing or opening the file?

If a file is downloaded from the Internet, and saved on disk, but is not opened by a user (if we keep autorun off), are there any chances that malicious code (e.g. a virus) in the file could trigger? ...
37
votes
2answers
16k views

What malicious things can happen when clicking on links in email?

I've received a spam from one of my friends (well I'm sure he didn't send it). so there's this link, and i'd thought what exactly would be the implications of clicking the link (i've not clicked it ...
36
votes
7answers
208k views

How can I watch porn, safely, and not get a virus? (and not infect corporate data also)

I'm part of a small office in the middle of nowhere, and we just got absorbed into a large mega corporation. Sometimes we watch porn, at the office, on company computers, using the company Internet....
27
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4answers
61k views

How to inject executable, malicious code into PDF, JPEG, MP3, etc.?

I wanted to know if its generally possible to inject executable code into files like PDFs or JPEGs etc., or must there be some kind of security hole in the application? And if so, how would one do ...
27
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4answers
2k views

Are anti-virus companies companies regularly committing software piracy?

As Mikko Hypponen highlighted in a recent tweet, anti-Virus companies collect and store both samples of malicious software and samples of legitimate software: This got me to thinking, what ...
23
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4answers
7k views

Are popular porn sites more likely to be infected with malware?

I'm trying to help my friend understand this because he believes that since a site is very popular, that it's less likely to infect its viewers because of its security! Is a popular site less likely ...
22
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4answers
5k views

Suspicious JavaScript in website header

I am not sure if this is the correct place to ask a questions such as this, apologies if it isn't. I have found the below code in the header of one of my wordPress websites, I am pretty sure it is ...
22
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3answers
4k views

Is it possible to transfer a virus through browser video?

I know that there is already a question related to viruses in videos, but the implication in the other question is that videos in question have been downloaded and played by media software on the ...
21
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5answers
1k views

Why would a virus writer bother to check to see if a machine is infected before infecting it?

I was looking at the tripartite structure of a virus, and it seems to check to see if a computer is infected before infecting it with the virus. Would this be an attempt to use files that are already ...
21
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2answers
1k views

Cohen's problem

Fred Cohen determined theoritically that viral detetction is an undecidable problem. Can anyone provide an intuitive reasoning for that? Background Fred Cohen experimented with computer viruses ...
21
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2answers
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How does a crypter for bypassing antivirus detection work?

I am talking about crypters used to encrypt files like viruses and keyloggers for the sole purpose of bypassing antivirus detection. How do they work?
21
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3answers
2k views

Are older viruses removed from virus definition files?

Antivirus software receives constant updates in the form of virus definition files, containing the patterns used to identify viruses. It is a feature present on most (if not all) major AV for at least ...
20
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8answers
12k views

Can malware be attached to an image?

I have a small number of employees who use a company computer but these people aren't very tech savvy. They use an email client and a messaging client. I'm pretty sure they wouldn't click on .exe or ....
20
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3answers
4k views

How can I tell if I have the citadel virus without downloading an antivirus?

I recently received an e-mail from Virgin Media indicating that I might have the Citadel virus. It obviously sounds like a fake e-mail, but I am almost certain it is genuine, as they had my name and ...
20
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6answers
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Malicious Links that Respond to Browsers but not curl or wget

There are some emails with links to people's cracked websites with a malware download Like this kind of email: fake DHL pack station email ... the links often take the form of: http:// www....
20
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4answers
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Is VLC on Linux vulnerable to an attack from .wmv files designed to install viruses? [duplicate]

I was stupid and did not check a video file I downloaded from an untrustworthy source. It was .wmv file with no readable properties of the video. I know that .wmv videos can download viruses. What I ...
20
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2answers
1k views

Could once infected machine be ever trusted again?

I'm just about to switch to a new SSD drive, so I figured it's a good occasion for a really, really fresh start. I reconsidered every installed piece of software, uninstalled lots of crap (...
19
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5answers
3k views

Is it possible for a file that is non-executable and read-only to run malicious code?

On a POSIX system, is there a possibility for a file which is non-executable and read-only (aka with a mode 444) to run malicious code on a machine? If so, can you explain how it would do so?
19
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5answers
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Find Virus in an Image File

I just received a .jpg file that I'm almost positive contains a virus, so i have two questions about what I am able to do with the image. My first question originates from the fact that I opened the ...
19
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5answers
3k views

Dualbooting Windows and Ubuntu, can I get Windows viruses/malware while running Ubuntu?

Today I have both Windows and Ubuntu installed on my SSD. What happens if I for some reason get a malware/virus (targeted for Windows), perhaps downloading something I should not, while I am running ...
19
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6answers
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Why do malware creators use such clever technologies for such silly purposes?

Some days ago I got infected by a malware, probably something new and very clever, as it went in unstopped and no scanning tool was able to detect it afterwards (see this question). It was a two-...
18
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7answers
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How to deal with a person who gets easily fooled by internet and mail scams?

alternative title: How to deal with a person who has gotten paranoid and doesn't want to go online anymore? A person, who has over the years been scammed many times, by bad spam/fraud emails, and ...
17
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4answers
10k views

Can Cryptolocker (Or Other Ransomware) Encrypt Files That Are Already Encrypted?

If you have already encrypted files, are they still vulnerable to being encrypted a second time by a program like Cryptolocker, or would this protect them?
17
votes
2answers
956 views

Is there a real possibility of getting malware by “drive-by”?

I know malware can be gotten by downloading and running stuff, but is there a real possibility of just viewing a webpage or clicking a link and getting one? Assuming using only Firefox / Chrome and ...
17
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4answers
5k views

What is the corrupted image vulnerability? How does it work?

What exactly happens when someone injects malicious binary code into an image file (on Windows)? How is that done?
17
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2answers
527 views

Do the most common ransomware programs delete the original files as they go, or in a big bulk delete at the very end?

I'm talking about the most common varieties like Cryptolocker, Cryptowall, Torrentlocker, KeRanger, RSA4096, etc. (There is not necessarily a need to answer for all of these, one or two may do.) If ...
16
votes
3answers
8k views

Do I really need an Anti-Virus software if I'm careful about where I browse?

A friend told to me the following: I don't use Anti-Virus software at all, I am just careful about where I go and what I click on. I've also heard this from other people as I've repaired their ...
16
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6answers
9k views

Finding a specific malware sample for malware analysis purposes

I wish to analyze the changes made by a specific virus. For example, Win32.Sality. Where can I get the sample of this, or other similar, malware for testing?
16
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4answers
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How is a worm different from a virus?

In spite of various online articles, I'm a bit unclear on the distinction between a "worm" and a "virus". Two related questions-- Is there a useful and clear distinction here or no? If so, what is ...
15
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4answers
13k views

What does this javascript file do? Is this a virus?

While searching on Google I found a website that shows one set of content to the Google Bot and an other to users (by redirecting to a new domain), and also a very suspicious Javascript file. Maybe it'...
15
votes
7answers
11k views

how to protect my USB stick from Viruses

I repair a lot of computers with viruses, malware, and what not, and I have one problem that I am struggling to find a solution for. Whenever I connect my USB stick that has the tools I need for the ...
15
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4answers
80k views

CryptoWall 3 - how to prevent and how to decrypt?

My father's computer is now infected with CryptoWall 3, according to the link below. http://www.bleepingcomputer.com/virus-removal/cryptowall-ransomware-information#CryptoWall Is there a way to ...
13
votes
3answers
5k views

What file formats are known to be unsafe?

I recently found out pdf's can contain viruses, and from the impression I got its more than a buffer overflow error (I heard it may visit urls automatically but the person sounded unsure) What are ...
13
votes
3answers
998 views

remote desktop connection to a potentially compromised machine

I am using rdesktop client on Linux to connect to windows machines. If some of these machines were compromised by some evil malware/virus/worm/trojan, is there any way for the malware to "jump" to my ...
12
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5answers
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Detection and analysis of unknown malware

Suppose I have a binary which is suspicious. How can I determine whether it is malicious, and if it is, reverse-engineer how it works and what it does? For example, maybe using static analysis? Are ...
12
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3answers
3k views

Am I protected from USB autorun malware on Windows 7?

As far as I know, the autorun.inf problem (the possibility of automatically executing code when a USB stick is plugged in) was solved through Windows Updates for XP, and on 7 it is no longer possible ...
12
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3answers
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FTP hacked, planted file [closed]

Can anyone help me to understand what this does? Someone has planted a file with this piece of code on my server.It is shortened because it cannot fit the question, but just to have some idea what ...