the principles and operation of computer security according to the present invention may be better understood with reference to the drawings and the accompanying description . the general concept of the present invention is to run several untrusted digital files simultaneously in one sandbox . because the overwhelming majority of untrusted files in fact do not contain malware , almost all such sessions end with no malicious activity detected , and the files are designated as trusted or benign . as soon as malicious activity is detected , the set of files being inspected is divided into two or more subsets and the subsets are inspected individually . this process is iterated until the file or files that contain malware have been identified and marked as malicious . at this point , the file ( s ) that contain malware may be inspected again in the conventional manner , to provide a complete report of attempted malicious activity and to provide clues to new malware patterns . other things being equal , the most efficient way to implement this method is to start with a number of untrusted files that is equal to a power of 2 . if malicious activity is detected in a set of 2 n files , where n & gt ; 0 , the set is divided in two and the two subsets are tested individually . this procedure is iterated until the file or files that contain malware are identified and are marked as malicious . if some of the files of a set of untrusted files are known a priori to make more intensive use of system resources than the other untrusted files , it may be more efficient , upon detecting malicious activity , to divide the set into two subsets with unequal numbers of files for further inspection , or even into three or more subsets . if latency is an issue , then , after the initial collective inspection of the set of untrusted files , each file of a subset is run in its own respective sandbox . a session of simultaneously running several files may be terminated as soon as malicious activity is detected ( which indicates that at least one of the files contains malware ), or may be allowed to run to completion in the conventional manner , followed by log inspection . whether or not the session is allowed to run to completion , the log may provide a clue as to which file is the malicious file . for example , if the sandbox operating system is a microsoft windows ™ operating system then the process id of the parent of the process that attempted malicious activity may indicate which file is most likely to be the malicious file . that file then is inspected separately . under some favorable circumstances , the process id of the parent process indicates with certainty which file is the malicious file , so that the simultaneous run may be terminated upon the appearance of such attempted malicious activity in the log and the identification of the responsible file ( and it is the unpredictability of such circumstances that mandates the iterative nature of the present invention ); but allowing the run to run to completion provides further clues about new malware , as described above . alternatively or additionally , the clue is used to identify files that were inspected in the session that could not have produced the logged malicious activity , and these files are marked as trusted and are not subjected to further inspection . referring now to the drawings , fig1 is a flow chart that illustrates the general concept of the present invention . a set 12 of one or more untrusted digital files is inspected in a sandbox 14 . if ( decision block 16 ) the sandbox session detected no attempted malicious activity , all the files are marked as benign in block 18 . if ( decision block 16 ) the sandbox session detected attempted malicious activity , then ( decision block 20 ) if set 12 includes only one file then that file is marked as malware in block 22 . otherwise , set 12 is split into two subsets 24 and 26 and the process is repeated separately for each subset . fig2 is a high - level partial block diagram of an exemplary computer system 30 configured to implement the present invention . only components of system 30 that are germane to the present invention are shown in fig2 . computer system 30 includes a processor 32 , a random access memory ( ram ) 34 , a non - volatile memory ( nvm ) 36 and an input / output ( i / o ) port 38 , all communicating with each other via a common bus 40 . in nvm 36 are stored operating system ( o / s ) code 42 and sandbox code 44 of the present invention . sandbox code 44 is conventional sandbox code modified to inspect several untrusted digital files simultaneously according to the principles of the present invention . under the control of os 42 , processor 32 loads sandbox code 44 from nvm 36 into ram 34 and executes sandbox code 44 in ram 34 to inspect sets of untrusted digital files that are received at i / o port 38 . as described above , the execution of sandbox code 44 sets up one or more sandboxes within system 30 for the simultaneous inspection of the files of each set . files that pass inspection are marked benign and are stored in nvm 36 and / or exported via i / o port 38 . files that fail inspection are deleted . one aspect of sandboxes that should be emphasized is that a sandbox running on a host computer sets up an entire virtual computer , including a virtual operating system , virtual random access memory , virtual input and output , etc . for running untrusted digital files . so , for example , a sandbox running on a host computer with a linux ™ operating system could set up and run a virtual computer whose operating system is microsoft windows ™. code 44 that runs several untrusted digital files simultaneously directly under o / s 42 would not be sandbox code of the present invention but instead would be more like code that runs the untrusted digital files simultaneously in separate individual respective sandboxes . nvm 36 is an example of a computer - readable storage medium bearing computer - readable code for implementing the data validation methodology described herein . other examples of such computer - readable storage media include read - only memories such as cds bearing such code . while the invention has been described with respect to a limited number of embodiments , it will be appreciated that many variations , modifications and other applications of the invention may be made . therefore , the claimed invention as recited in the claims that follow is not limited to the embodiments described herein .