Information about the virus

Computer viruses are usually divided into the following categories:

Boot sector virus

Archival virus

Big virus

Other new viruses

Information provided by the Information Technology Services Department of the Government of the Hong Kong Special Administrative Region.

Boot sector virus

Before the mid-1990s, boot sector virus was the most common virus type. This virus is hidden in the main boot sector of the infected hard disk drive or the boot sector of the disk operating system. When a floppy disk is inserted into an infected personal computer, the virus will infect the boot sector of the floppy disk, thus spreading the virus.

When an infected floppy disk is used to start the process, the computer will be infected. In the process of starting the computer, the basic input and output system will execute virus coding in the boot sector of the floppy disk, so the system will be controlled by the virus instead. After the virus controls the computer system, it will write the virus code into the main boot sector of the hard disk. After that, the normal startup procedure will be resumed. From the user's point of view, everything seems normal.

When the computer is started in the future, the virus residing in the infected main boot sector will start to run. So the virus will enter the memory and can infect other used floppy disks at any time.

【 The main boot sector is the first sector of the hard disk, which contains the partition control table and the code for executing the operating system. Sectors above 16 behind the main boot sector are usually empty.

A hard disk can be divided into four storage partitions at most, and the extended partition of the disk operating system can be subdivided into multiple logical drives.

The first sector of each partition is the boot sector, which contains the data and code of the operating system loaded into the partition.

The floppy disk has no main boot sector. The floppy disk formatted in the standard disk operating system format is structurally the same as the disk operating system partition of the hard disk. ]

Archival virus

A file virus is a virus attached to a file and spread through a program file rather than a data file. When a computer runs an infected program, it will be infected. These infected programs may spread through floppy disks, CDs, the Internet and other channels. After the infected program is executed, the attached virus will infect other programs immediately, or it may become a resident program to infect other programs in the future. After these steps are completed, the virus will resume its normal program. Therefore, it is not easy for users to find any abnormal situation when executing infected programs.

File viruses usually infect files with specific file extensions. Files with extensions of COM, EXE and SYS are common virus infection objects.

Big virus

1In July, 1995, a new computer virus was discovered, which immediately shocked the computer world. This new virus is called macro virus, which is different from the viruses that have always appeared. It can infect data files instead of executable files. In fact, this is not a new concept, because the feasibility study of writing viruses in macro language began in the late 1980 s. Macro viruses that appear in Word programs can run on many different operating platforms. As long as the computer Word program supports Word file format, it is likely to be infected. In other words, whether you use an OS/2 or Windows version of Word program, a personal computer or a Macintosh computer, you may be infected by macro virus.

Other new viruses

Viruses and anti-virus technologies are constantly changing and changing with each passing day. As computer users use new operating platforms/computer technologies, people who write viruses will develop new viruses and then spread them. The following are some new operating platforms/computer technologies where new virus types may appear:

Java language (a computer language, especially for creating websites)

ActiveX networked multimedia object technology advocated by Microsoft

Visual Basic (VB) script

Hypertext markup language

email/messaging system

Java language (a computer language, especially for creating websites)

Java virus has always been a controversial topic: can Java virus be written? Will Java virus spread between computers or through the Internet? The above problems have been discussed in different news groups. Because Java micro-applications are designed to run in a controlled environment (called "sandbox"), there is no access to computer files or network connections, so the possibility of Java virus spreading between computers is extremely low.

However, because Java, like other standard programs, allows developers to build applications that can control the whole system, there is room for the emergence and existence of Java viruses.

The first virus discovered based on Java computer programming language is called "Java". StrangeBrew”。 First discovered in1September, 998, it infects files belonging to the Java category. But this virus only affects independent Java application files, and files running as micro-applications will not be infected. Although Java applications are not common, and "Java. The "StrangeBrew" virus is only in its initial stage, and its influence cannot be ignored. With the increasing popularity of Java applications, it is expected that the types of Java viruses will gradually increase.

ActiveX networked multimedia object technology advocated by Microsoft

Like Java, ActiveX is considered as an operating platform that will be invaded by viruses. If we compare the two in design, ActiveX is more likely to spread viruses than Java. Basically, ActiveX is a simplified version of Object Linking and Embedding (OLE). It will directly contact the computer's Windows system, so it can connect any system function. In addition, the users of ActiveX are not limited to users of MS Internet Explorer; Now, plug-ins of Netscape Navigator can also use this technology. In contrast, Java is executed in a "controlled environment" or through a program called a "Java virtual machine", so Java can be separated from the services of the operating system.

Visual Basic (VB) script

In the past, people who wrote viruses had to have a good understanding of the basic operation of computers if they wanted to successfully write a virus that could infect other computers. However, with the appearance of macros in Microsoft Office, the tools for writing viruses are ready, and the writers do not need much information technology knowledge to be competent. Similarly, the operating environment in which VB script virus works will soon become popular and spread easily.

VB script virus has posed a real threat to computer users. The original intention of Microsoft is to include a powerful and easy-to-use language to access the resources in Windows 98/NT system conveniently. VB script is written in a human-readable way, so it is easy to understand. It is for this reason that many virus writers who do not have advanced information technology knowledge can also invade this field.

The first generation virus of the program written with VB script is hidden in the webpage written with HTML and spread through the Internet. At present, viruses written by VB scripts with strong spread usually spread by sending emails, and virus programs are sent together according to the email addresses listed in the user's address book. When users run the attached program, it will help the virus spread.

Hypertext markup language (HTML)

Viruses spread through HTML is another topic widely discussed on the Internet. Some people even claimed/announced that they had invented/discovered the first virus belonging to the HTML category.

HTML is a programming language that controls the design of web pages. Originally, pure HTML will not be infected, so browsers that only support HTML will not be in danger of being infected by viruses. The so-called "HTML virus" is really rare. Therefore, the real threat comes not from browsing the web pages of the Internet, but from downloading and executing programs with infected virus codes from the Internet.

However, at present, most browsers support other languages to write web pages, and the so-called "HTML virus" usually spreads by writing texts in these languages. Viruses in texts usually infect computers through web pages and VBS. Offline is a typical example. At present, the most common text virus is the VB script virus just discussed.

email/messaging system

Lotus Notes has a large number of users, and it will be the software targeted by people who write viruses. Although the local Lotus Notes virus has not been found, the rich text fields in the Lotus Notes database provide hiding places for traditional viruses, such as file viruses and macro viruses. Because the related records have been compressed, general antivirus software can't detect the virus in Notes database. In order to prevent computer viruses from invading the running environment of Notes, we suggest that users install anti-virus software specially designed for Notes software.