Wassim Masood has been the webmaster for Woori Finance only ten days when Woori's website was flooded with access attempts. Wassim shut down the site and only opened it to Web addresses which he specifically identified as legitimate. As a result, many of Woori's customers were unable to obtain loans, causing Woori to lose a significant amount of business. Woori Finance suffered from a
a. malware attack.
b. denial-of-service attack.
c. cyber-extortion attack.
d. zero-day attack.