These are not dangerous memory resident parasitic polymorphic viruses. They hook INT 21h and write themselves to the end of EXE files that are executed.
Depending on the system date "Hydra_II.1162" displays:
This is Hydra v1.0.
Don`t panic, I will not destroy your data.
If the day number is equal to the month number "Hydra_II.1649" manifests itself with a video effect and then displays the message:
This is Hydra v1.1.
Don`t panic, I will not destroy your data.
