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Details
Phoenix Family
These are very dangerous resident polymorphic parasitic viruses. They write themselves to the middle of COM files that are executed or closed. They write to the end of EXE files the trojan program that in some cases erases all information on installed hard disks.
"Phoenix.Proud,Live" infect COM files only, "Phoenix.Live.a" does not infect COMMAND.COM.
While infecting a COM file the virus reads the data from the middle of the file, saves it to the end of the file, and then overwrites the data in the file middle with its copy and writes Jmp-Virus command to the beginning of the file. While infecting COMMAND.COM the virus writes itself to the the stack area of COMMAND.COM, and the file length does not grow.
Infection of COM file Infection of COMMAND.COM file
+-----------+ +-----------+ +-----------+ +-----------+
¦ File ¦ ¦ File ¦ ¦COMMAND.COM¦ ¦COMMAND.COM¦
¦ ¦ ¦ ¦ ¦ ¦ ¦ ¦
¦ ¦ ¦ ¦ ¦ ¦ ¦ ¦
+ - - - - - ¦ +-----------¦ + - - - - - ¦ +-----------¦
¦ ¦--+ ¦ Virus ¦ ¦ ¦ ¦ Virus ¦
+ - - - - - ¦ ¦ +-----------¦ + - - - - - ¦ +-----------¦
+-----------+ ¦ ¦- - - - - -¦ +-----------+ +-----------+
+-->¦ ¦
+-----------+
The viruses also hook INT 13h and then, depending on some preconditions, randomly rearrange bytes in information blocks being read from, and written to disks.
The viruses of the family for the first time uses two new methods. First, the viruses intercept DOS calls to the files by using INT 2Ah instead of INT 21h. Second, the viruses (except "Phoenix.Live.a") are polymorphic and do not have any constant mask (signature): the main part of the virus is encrypted, and a decoding program (32 bytes long) is selected from 204 possible variants (one have to bear in mind that these viruses have the following lengths: "Phoenix" - 1704 bytes, "Phoenix.Evil" - 1701 bytes, "Phoenix.Proud" - 1102 bytes).
The viruses contain the text strings:
"Phoenix": PHOENIX
"Phoenix.Evil": The evil that men do lives on and on and onall
"Phoenix.Proud": Proudly made in Sofia
"Phoenix.Live.a,b": Live after Death |
