Collectively, these systems provide vital links between the exchanges, NASD, and their customers by routing orders to buy or sell stocks and options, reporting executed trades, or providing current stock pricing data to the financial marketplace. Although the risk of successful external virus attacks appear relatively low, a number of internal control weaknesses at the exchanges' and NASD's computer centers were found. These weaknesses pose risks of an insider threatening the systems by introducing security intrusions -- such as a virus -- without being detected. Recommendations include (1) proper correction of the weaknesses found; (2) expansion of information security administration programs; and (3) assessment of the exchanges' and NASD's computer security practices.