Cryptolocker (was RE: Is tape dead?

jwsmobile jws at
Wed Sep 16 22:56:03 CDT 2015

On 9/16/2015 6:36 PM, Jon Elson wrote:
> On 09/16/2015 01:29 PM, Paul Koning wrote:
>> I never had any incentive to look for holes in CDC operating systems, 
>> but I still remember a simple hole I found in OS/360, about a month 
>> after I first wrote a program for that OS. It allowed anyone to run 
>> supervisor mode code with a couple dozen lines of assembler source 
>> code. I found it on OS/PCP 19.6, but I noticed in graduate school 
>> that it still worked on the university's 370 running OS/MVS 21.7. 
>> (The magic? Use the OS service to give a symbolic name to a location 
>> in your code, with a well chosen name, then give that name as the 
>> name of the "start I/O appendage" in an EXCP style I/O request.) paul 
> Yup, the classic breakin was you set up an exception handler with SPIE 
> (specify program  interrupt exit, I think) and then do a divide by 
> zero.  This gives the handler the PSW of the problem program. You turn 
> the P bit of the PSW off and return.  The stock OS would actually 
> ALLOW you to DO this, and just return to the user program now in 
> supervisor state!  It was a VERY simple fix, you just don't allow any 
> exception handler to change the state of the P bit.  But, MANY systems 
> did not do that check.
The SPIE fix was fixed in MVT 21 which we ran at UMR in my memory before 
I left in 75.  I know of at least three of us who wrote up exploits, 
which stored the PSW to show supervisor state, and let it go at that.  
That was on the UMR 360 / 50

The really fun "trojan" was a console logger that was around which 
watched the MVS VS1 console screen for changes and rendered a scrolling 
rendition of the log on a terminal.  The computer operators at our 
remote site didn't have that working with their remote Hasp workstation, 
only had the entries pertinent to locally submitted jobs.  This was on a 
370 / 158 at University of Missouri, Columbia.

Also there was a password logger which watched all the TSO logins, and 
logged the password and account for every user.  That exploit still 
existed when I left.  The IBM code had an 8 byte double word in which it 
stored a "scrambled" version of the password for use by jobs that needed 
authentication (way before RACF or such) and could verify w/o 
re-prompting a lot for the password.  However when you entered your 
password the first 8 characters, which were all that were used for 
authentication were stored for a few cycles in that same word.

So to get the password, you watched the login state, and as long as the 
process was logged off, the entry was zero.  You would grab the values 
and store the first value that appeared after it went non zero and about 
99% of the time it was the clear text.

Fun times.
> So MANY other weaknesses could easily be caused by accident.  Like, 
> the file that contained valid account numbers was often not 
> protected.  Anybody could just print out that file.
> Jon

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