Malware Versus Anti-Malware

A computer virus is programmed to make three identical copies of itself and then delete itself. Network anti-malware software has a probability P of destroying any given copy of the virus before it can make the three copies. A single copy of it is introduced into the network. What is the minimum value of P so that there is 99 percent chance that the virus will be completely eradicated eventually? What is the minimum value of P for a 100 percent chance of eventual complete eradication?

Crack the Code

The coded message was:

“NQV ARC RMWQLP ATXPROCMN FOC R YOMMOQC KQMMRXL OU NQV LPRXP FOPH QCT KQMMRX RCK YTP R LWRMM TCQVIH UXRAPOQC TCQVIH POWTL.”

It decodes to:

“YOU CAN ALMOST CERTAINLY WIN A BILLION DOLLARS IF YOU START WITH ONE DOLLAR AND BET A SMALL ENOUGH FRACTION ENOUGH TIMES.”

Decoding this is a matter of educated guesswork, process of elimination, and focusing on decoding the vowels in short words. Generally, the first step is to notice that the one letter coded word “R” must decode to either “A” or “I.” Since it appears twice in the middle of the message “A” is a better guess. That limits the possibilities for the vowels in the two letter and three letter words.

Solutions were also submitted by Patrick Allen, Neil Bethel, Peggy Cheng, Lance Clevenger, Bob Conger, Todd Dashoff, George De Graaf, Mario DiCaro, Daniel Eklove, Joey Janzen, Rob Kahn, Sze Qi Lai, Luc Langlois, George Levine, Kristain Lindemann, Daniel Mackey, Sharon Markowski, Juan McNamara, Jim Muza, Richard Newell, Dave Oakden, Jeff Prince, Damon Raben, Dave Schofield, Gregory Scruton, Bruce Spidell, Tony Strazzara, Marla Strykowski, Jeff Subeck, Kathleen Tierney, Sonja Uyenco, Leslie Vernon and Walt Wright.

AR Puzzle Editor Jon Evans is president of Convergent Actuarial Services, Inc. in Delray Beach, Florida.