subject

C6 - In accepting the ACM Turing Award, Ken Thompson described a devious Trojan horse attack on a Unix system, which most people now refer to as Thompson’s rigged compiler. This attack first changes the binary version of the login program to add a backdoor, say, to allow a new user, 12345, that has password, 67890, which is never checked against the password file. Thus, the attacker can always login to this computer using this username and password. Then the attack changes the binary version of the C compiler, so that it first checks if it is compiling the source code for the login program, and, if so, it reinserts the backdoor in the binary version. Thus, a system administrator cannot remove this Trojan horse simply by recompiling the login program. In fact, the attack goes a step further, so that the C compiler also checks if it is compiling the source code of the C compiler itself, and, if so, it inserts the extra code that reinserts the backdoor for when it is compiling the login program. So recompiling the C compiler won’t fix this attack either, and if anyone examines the source code for the login program or the C compiler, they won’t notice that anything is wrong. Now suppose your Unix system has been compromised in this way (which you confirm by logging in as 12345). How can you fix it, without using any outside resources (like a fresh copy of the operating system)?

ansver
Answers: 2

Another question on Computers and Technology

question
Computers and Technology, 22.06.2019 06:30
What result from the passage of this amendment
Answers: 1
question
Computers and Technology, 22.06.2019 09:00
Howard is designing a chair swing ride. the swing ropes are 5 meters long, and in full swing they tilt in an angle of 29° outside chairs to be 2.75 m above the ground in full swing.
Answers: 1
question
Computers and Technology, 23.06.2019 07:30
What key should you press and hold to select and open multiple files at one time? enter alt control esc
Answers: 1
question
Computers and Technology, 23.06.2019 10:20
Suppose there is a relation r(a, b, c) with a b+-tree index with search keys (a, b).1. what is the worst-case cost of finding records satisfying 10 < a < 50 using this index, in terms of the number of records n1, retrieved and the height h of the tree? 2. what is the worst-case cost of finding records satisfying 10 < a < 50 and 5 < b < 10 using this index, in terms of the number of records n2 that satisfy this selection, as well as n1 and h defined above? 3. under what conditions on n1 and n2, would the index be an efficient way of finding records satisfying the condition from part (2)?
Answers: 1
You know the right answer?
C6 - In accepting the ACM Turing Award, Ken Thompson described a devious Trojan horse attack on a Un...
Questions
question
World Languages, 27.09.2019 05:30
question
Health, 27.09.2019 05:30
question
Mathematics, 27.09.2019 05:30
question
English, 27.09.2019 05:30
question
Geography, 27.09.2019 05:30
question
Mathematics, 27.09.2019 05:30
question
Mathematics, 27.09.2019 05:30
question
Mathematics, 27.09.2019 05:30
question
Mathematics, 27.09.2019 05:30