Virus & Antivirus in Linux

Part 1:

All windows users would have heard about computer virus and anti-virus software’s and the first thing they do is install a anti-virus software in their computer. Often, the buzz in the Windows security world is about which protection-for-profit firm was the first to discover and offer protection for the malwares.


If a rogue program gets in your windows machine, the time and money you have to invest to remove those malwares not only helps to reinforce the notion that you have to have malware protection, but that it has to be the right protection, too. The security firms are aware of this and they play on hte security fears of the end-user in their advertising. The huge amount of malware available for windows and the way windows user permissions works has conditioned Windows users to accept this security tax.


It is no wonder when Windows users who are finally convinced to try Linux are in disbelief when I tell them to lay that burden down. The first question they all ask is whether Linux is virus proof and is it true that it doesn't need an Anti-virus software? My answer to that question is no. Linux is not virus proof, but the way user permission are played out and considering the number of malwares available for Linux, the role played by the Anti-virus software is negligible and downplayed in a Linux environment.


User permission on Linux

Linux implements a multi-user environment where users are granted specific privileges, due to this, to gain control over a Linux system or cause any serious damages to the system itself, the malware would have to gain root access to the system. To be clear just remember permissions on Linux are universal. They cover three things you can do with files: read, write, and execute. Not only that, they come in three levels: for the root user, for the individual user who is signed in, and for the rest of the world. By default system files can only be accessed as root user, while a normal user can have permission to read, write and execute his files alone and others can access or read the users file only if the user have given permission for them to do so. Normally in a Linux environment no user is given root permission to access system files. Because of this a malware needs root permission to have an impact on the system as a whole.


Virus in Linux environment

No, virus are environment dependent and they have limited life time. Like any biological entity, a computer virus needs to spread(reproduce) before it dies to successfully cause an outbreak. Due to the hostile nature in Linux, a virus life is short and dies before it can cause any significant damages. Also due to the difference between the binary/executable files between Windows and Linux, Windows virus has no impact on a Linux machine, and virus writers have to spend significant amount of time to create a Linux virus that can survive the hostile environment of Linux. Because of this only a couple hundred of Linux viruses are in the open (Windows has over a million malwares) and those available too have problems in taking control of an entire system.


Some malware programs require that you open an attachment. Others don't even require that user error. On Linux, there is built-in protection against such craft. Newly deposited files from your email client or Web browser are not given execute privileges. Cleverly renaming executable files as something else doesn't matter, because Linux and its applications don't depend on file extensions to identify the properties of a file, so they won't mistakenly execute malware as they interact with it. Due to this only users who tries to execute all the programs as root are those who likely get a malware to control the system. But fortunately most of the Linux users are either geeks who know what they are doing or those who even don't know how to execute a program as root. This also makes Linux a place for a virus.


Another thing to note is the software repositories used by Linux. These repositories contain all the software’s that can run in Linux and are maintained by Open Source communities and are often checked thoroughly for malware. Also most of the Linux programs or software’s are available as open-source, meaning the source code is available and the executable can be compiled and installed, thus further reducing any chance of malware.


So, is Linux virus proof?


No. But the number of viruses and the damage they can make are insignificant. Linux users, like users on every operating system, must always be aware of security issues. They must act intelligently to keep their systems safe and secure. They should not run programs with root privileges when they are not required, and they should apply security patches regularly.

Part 2: Types of Malware and how they can infect you

In the previous article we discussed about how virus has a hard time in Linux OS due to its permission system. In this article we will see the different malwares available for Linux and how they affect your system and conclude our two part article on Virus & Anti-virus in Linux.

Viruses and Trojan horses

Although there are only few Linux viruses available, it is always best to use free anti-virus scanners (like clam anti-virus) to scan the software’s you download from unknown sources. Because if the software is infected and was run with root permission, it will infect the whole system and cause enormous damages. Basically the false sense of security among the user's mind is what allows most Linux viruses to infect your system. There are some Linux distributions that allow users login as root by default (Lindows) and falsely advertise that they are secure. But the truth is any Linux OS that allows you to login as root by default is not secure than a windows 9x operating systems.
Ignorance Is Bliss

The lack of knowledge that is seen in first time Linux users makes their system more protected than most Linux users ans they don't know how to run a program or login as root by default. These type of users usually download software’s only from Linux repositories configured by that particular distro team.

For more accustomed users who use root login and download the software from many sources must be aware, that they must try to limit the habit of running unknown programs as root and if they have to then use a free anti-virus software for Linux and scan those executable's firs before running.

Remember as long as u don't run application as root and don't install software’s from website you don't know or trust, a Linux OS is much more safer than a Windows system with an anti-virus.

Worms and targeted attacks

The classical threat to Unix-like systems is vulnerabilities in network daemons, such as ssh and WWW servers. These can be used by worms or for attacks against specific targets. As servers are patched quite quickly when a vulnerability is found, there have been only a few widespread worms of this kind. As specific targets can be attacked through a vulnerability that is not publicly known there is no guarantee that a certain installation is secure. Also servers without such vulnerabilities can be successfully attacked through weak passwords.

WWW scripts

Linux servers may also be used by malware without any attack against the system itself, where e.g. WWW content and scripts are insufficiently restricted or checked and used by malware to attack visitors. Typically a CGI script (meant for leaving comments) by mistake allows inclusion of code exploiting vulnerabilities in the browser.

Buffer overruns

Older Linux distributions were relatively sensitive to buffer overrun attacks: if the program did not care about the size of the buffer itself, the kernel provided only limited protection, allowing an attacker to execute arbitrary code under the rights of the vulnerable application under attack. Programs that gain root access even when launched by a non-root user (via the setuid bit) were particularly attractive to attack. However as of 2009 most of the kernels include address space randomization, enhanced memory protection and other extensions making such attacks much more difficult to arrange.

Cross-platform viruses

A new area of concern identified in 2007 is that of cross-platform viruses, driven by the popularity of cross-platform applications. This was brought to the forefront of malware awareness by the distribution of an Openoffice.org virus called Bad Bunny.

Social engineering

Linux is as vulnerable to malware that tricks the user into installing it through social engineering as other operating systems. In December 2009 a malicious waterfall screen-saver was discovered that contained a script that used the infected Linux PC in denial-of-service attacks.

Conclussion


As you can see most of the malwares discussed above need users permission or mistakes to take over a Linux System. And to give you an answer about is Linux is secure, yes most Linux distro's (that dont allow you to login as root )are secure than a Windows with basic antivirus software, but also remember, being secure doesn't mean bulletproof. So if your one of these people feeling secure, think about this next time you go online. There is no bigger security hole than the one between chair and computer. Always be careful on the internet, don't click on those links marked as dangerous(I know it sounds obvious), watch out with pop-ups and try to avoid running programs as root unless it is absolutely necessary.

Source:
http://www.primeinspiration.com/os/linux/security/20-virus-a-antivirus-in-linux-part-2-types-of-malware-and-how-they-can-infect-you.html
http://www.primeinspiration.com/os/linux/security/20-virus-a-antivirus-in-linux-part-2-types-of-malware-and-how-they-can-infect-you.html