Virus.DOS.Lokjaw.Firefly is a dangerous memory resident encrypted virus on DOS.

There are 5 variants in 2 versions, represented by the following:

  • Virus.DOS.Lokjaw.Firefly.778
  • Virus.DOS.Lokjaw.Firefly.1087


When the virus is loaded into memory, it hooks INT 21h to infect any DOS executable that is run.

The actual infection size of Lokjaw.Firefly.1096 is 1,106 bytes.

Memory usageEdit

The following table shows the memory usage of the variants.

Variant Memory usage in bytes
Lokjaw.Firefly.778 4,096
Lokjaw.Firefly.1087 4,096
Lokjaw.Firefly.1096 4,096
Lokjaw.Firefly.1097 4,096
Lokjaw.Firefly.1107 4,096


This virus has two payloads which will be activated after loading into memory.


This is the only harmless variant, it switches the status of NumLock, CapsLock and ScrollLock, which are visible by observing the status indicators on the keyboard.

Lokjaw.Firefly.1087, 1096, 1097 and 1107Edit

In addition of switching the status of the key input locks, the virus also detects whether a file to be run or opened has the filename:


If yes, it deletes the file and displays the following message:

Bad Command or file name

Which is same as that in Jerusalem.

Any file having this name in any type will be deleted by the virus when it is opened, in attempt to delete anti-virus files.


This family has 5 variants in total:

  • Virus.DOS.Lokjaw.Firefly.778
  • Virus.DOS.Lokjaw.Firefly.1087
  • Virus.DOS.Lokjaw.Firefly.1096
  • Virus.DOS.Lokjaw.Firefly.1097
  • Virus.DOS.Lokjaw.Firefly.1107

Other detailsEdit

Every variant contains the internal text string:

[Firefly] By Nikademus
Greetings to Urnst Kouch and the CRYPT stuff.

Lokjaw.Firefly.778 contains the internal text strings:

Happiness in Slavery
The land of Rape and Honey

Lokjaw.Firefly.1087 contains the internal text strings:

American Jesus
Dont pray on me
Recipe for hAte
Atomic Garden
Its Dead Jim

Lokjaw.Firefly.1096, 1097 and 1107 contain the internal text strings:

Psalm 69
Every day is Halloween
Happiness in Slavery
The land of Rape and Honey
Its Dead Jim


  1. List of variants of the Lokjaw.Firefly virus on VX Heaven

See alsoEdit




Firefly virus review by danooct1

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