Viruses aiming at Linux

In the era where computer viruses are getting more and more rampant, computer users have to suffer from virus attacks. As we all know, the virus-stricken computer may run slower and slower, and even crash. Moreover, users may fail to access and manage needed files. Therefore, computer users are supposed to get familiar with the commonly seen types of computer viruses, corresponding symptoms and precautious methods. Here, the viruses aiming at Linux system are introduced. Also, effective methods against those viruses are recommended.
1. Viruses for ELF files Aiming at ELF files, certain kind of viruses written with assembly language or C programming language are of high risk to ELF file security in Linux. Lindose is one of certain viruses. After finding an ELF file, Lindose will check the model of the machine. If the model is Intel80386, Lindose will check whether there is a part whose size is larger than 2784 bytes in the file. If there is, Lindose will overwrite the part with its own codes, and then add corresponding codes of cover object. At the same time, Lindose will point the entrance of cover object to virus codes.
Precautious methods: Viruses for ELF files can transmit only after they get sufficient access rights, just because Linux owns rigorous access-control mechanism. Therefore, to prevent viruses for ELF files, Linux users ought to better control access to files. Moreover, do not operate unsolicited executable files with root account, so as to protect the whole Linux system from being infected.
2. Script viruses Script viruses refer to the viruses written with scripting language such as shell. It is easy for hackers to write such kind of viruses even though they have limited relevant knowledge. Script viruses can delete files, destroy system normal operation and even download and install Trojan software. However, script viruses are of low infectivity, so they can only leave damage to local machine.
Precautious method: Linux users should not run unsolicited scripts. Also, strictly restricting the access right for root account is useful.
3. Worms under Linux Similar to worms under Windows, worms under Linux can run independently and spread to another computer by making use of the bugs existing in Linux system and service, such as Ramen. Ramen spreads based on the bugs: "rpc.statd" and "wu-ftp" in Redhat6.2 and 7.0 of Linux.
Precautious methods: As statistics suggest, the vast majority of worms under Linux spread based on published security bugs. Therefore, if users take timely and effective measures, they can be immune to certain kind of virus invasions. Unfortunately, Linux managers fail to get the latest information about the system and its service. Therefore, Linux users are expected to keep an eye on Linux bugs, and then take corresponding measures.
4. Backdoors Being active on Linux, backdoors are elusive, so it is hard for Linux users to wipe them out.
Precautious method: Linux users can resort to some software such as chkrootkit and rootkits to find out the worms and backdoors hidden in operating system and service.