For the equity trading system discussed in Section 13.4.2, whose architecture is shown in Figure 13.14, suggest two further plausible attacks on the system and propose possible strategies that could counter these attacks.

Question

What will be an ideal response?

Answer 1

Attack 1: Unauthorised orders are inserted into the system between the system and
the external computer system of the stock buyer or seller. That is, the
communications link between the system and the external world is
compromised.
Counter-strategies: Ensure that all orders are encrypted using a key that is known
only to the ordering system and the stock buyer/seller. Thus, additional
orders introduced into the system can be detected.
Monitor all orders transmitted on communication link and ensure that the number
of transmitted orders matches the number of placed orders.
Attack 2: Authorised insider places orders that could result in unacceptable losses
for the company (this has occurred in several real systems).
Counter-strategies: Ensure that authorised users have an order limit and this can
only be exceeded with approval from their manager. Monitor transactions of
all insiders to ensure that losses do not exceed limit. Provide daily lists of
insider transactions for checking.