SystemsSec 2018W Lecture 14

Audio

Lecture 14 audio.

Notes

► Many strategies are wrong: If there is one single bug in any major system we use, everything falls apart

► We can do better, but the way we do things now is not sustainable

→ Existence proof: Biology

1. Everything starts with a random process

2. How do biology systems protect itself again adversaries?

ANIMALS

• Animals face threats (ie. Falls of cliff, gets eaten)

• Threats from really small things (huge factor in mortality, ie. humans lifespan doubled because of disease control):

→ They see the animal as a resource, so why not use it?

→ Most important defence: Barrier defence

- Skin

→ But we can't keep everything out: Basic chemistry

- Stomach acid to react with what came into your body

- Digestive enzymes (enzyme: biological catalyst) breaks down proteins

• Analogies:

DNA = "Stored code"

→ Backbone = "Framework"

Proteins = "Running code"

T-cells = Has randomized detectors to find bad things. If binded to a regular cell, gets killed

→ Auto-immune disease

- T-cell recognizes some behaviour and reacts with it

- To prevent mistakes (ie. autoimmune disease)

○ Only battles when there is evidence cells are dying

VIRUSES

• Chunk of DNA/RNA (in between DNA/RNA and proteins) surrounded by proteins
• When comes in contact with cell, injects DNA into cell

- Overflow cell (cell running malicious code) until it explode, and continue to other cells

-Cells have vulnerabilities

□ Viruses targets fact that cells have semi-permeable membranes

- Defence

□ Cells have different membranes

IMMUNE SYSTEM

• Regular proteins will output certain peptide, immune system checks if its the right one

- Virus imitates the protein

• Red, hot: Immune system discovered dead cells and investigates
• Incompatible MHC: Organ rejects new organ

DIGESTIVE SYSTEM

• When your good bacteria turns bad, fecal transplant

The body is not an engineering system: Separation of concern is not there, they are all just cells.