Underlying concept

GL original notation

Farrow notation

Note

Sites or information set; unit of analysis

One unit

Multiple sites i

i = 1 for equivalence

Investment (expenditure) in cybersecurity

Z

e

Equivalent

Probability of successful attack given an investment level

S(z)

Security breach function

P(e)

Terrorism event function

Equivalent (but modified initial limits of prob. not incorporated in Farrow)

Conditional cost or loss of an event

L

Initially, L; later LP + LE for private and external

C(e)

Includes both direct and external, CP and CE

C = LP + LE

GL is constant

GL start with LP, Farrow starts with C = CP + CE = LP + LE and as a function of expenditures