Historical clue formulations

• Malware, often — 2021-06-23
• Mono, e.g. — 2018-12-15
• Bad strain? — 2014-08-07
• Email attachment attachment? — 2014-06-12
• Flu cause — 2013-06-17
• Hacking tool — 2011-09-18
• It may be written in code — 2010-10-16
• Common cold cause — 2010-03-22
• Computer woe — 2005-03-13
• Ebola, for one — 1999-12-05
• Flu cause — 1998-09-21
• Bug — 1997-02-07
• Bug — 1996-08-24