Trusted Flow for Malware Protection

1
Trusted Flow for Malware Protection

• F. Massacci

(DIT - University of Trento - www.dit.unitn.it)
2
Observation on Trust Boundaries

• Cheating Husbands and other stories (Fagin et
  al.)
• Corporate Network looks like an Harem
• Different hierachies of husbands (each with his
  privileges and precious jewelry)
• Bulky Guards at the door
• Spies and mail surveilance and censorship
• Bedchamber boys
• Enter Laptops and mobility
• Allow husbands to have sex in the (internet)
  bazar
• And then come back to harem carring malware with
  them
• They can become zombies controlled from outside
• Something clearly wrong here

3
Trusted Flow for Malware

• Solution Cut mobility, tighten entrance rule
• Not really possible
• So we must allow sex in the bazar
• Solution Check behavior of husband once inside
• Option 1 check clothes are untainted
• Digitally signed assemblies/software (eg .NET)
• Not very good show clean clothes at the door,
  use completely dirty dresses (eg latest rootkit,
  recent IAT attack on .NET by UniTN)
• Option 2 trusted flow for Malware

4
Implementing Trusted Flow for Malware

• Inoculation of Vaccines into husbands
• Injecting trusted flow into important sw once
  inside
• Give husbands obfuscated drinks on wedding day
• if vaccine spots keep appearing (trusted flow)
  fine
• else repudiate husband (isolate laptop from
  network)
• Unfortunately
• Smart husbands can always reverse engineer
  software
• Can tell original drink from inoculated drink
• Can make their own anti-vaccines give spots even
  if misbehaving

5
Implementing Trusted Flow for Malware 2

• Fortunately
• Normal husbands can only buy ready-made
  (automated) anti-vaccines from the bazar
• Smart husbands arent many and have better things
  to do
• than making anti-vaccines (or having sex in the
  bazar for that matter)
• Objective keep normal husbands from misbehaving
• Vaccines should be unique to each husband
• Vaccines should require human intervention for
  removal or bypassing