This is a benign memory resident parasitic encrypted virus. It hooks INT 21h and writes itself to the end of COM and EXE files that are executed (except COMMAND.COM). It looks like modifications of the "Jerusalem" virus. On June, 12th it displays the national flag of Philippines, the text message and then plays a tune:
June 12 - the Independence Day of the Philippines. MABUHAY ANG PILIPINAS! Dedicated to Manong Eddie.
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Virus.DOS.Mabuhay is a memory resident parasitic encrypted virus on DOS. The virus appears to...