Digital signature of software
August 9th, 2016
not digital signature but “valid” digital signature. anyone can sign a file with digital signature , there must be a counter signer(generally security firms) , to make it valid. those firms give certificate while signing it. a certificate have a time period to expire. while a file signed like i told , changes can not made on it . even if you do , you need to remove digital signature so file either will have no signature or invalid signature. mainly .exe and .dll files are digitally signed due to malicious nature of them
after explaining those let me tell you how to check if a file have it. right click an .exe file from a legitimate software , click properties then there should be a digital signature tab if file is signed. click that tab then select digital signature on the list and then click details just below of it.
a new tab will pop up , at the top of it there should be something called “digital signature information” under it there is an explanation. either “this digital signature is valid” or if it is invalid why it is invalid such as it has expired or there is a problem with certificate chain etc… only legit softwares have valid digital signatures , keep that in mind since you are asking this on a forum
at the last tab which pop up , there are many information along if signature is valid or not , such as expire time or other counter signers if there are more than 1 etc.. but you dont need to check them.
and ofc , it doesnt mean all .exe files without digital signature is malicious but an .exe with valid digital signature is safe for %99.9999 , although it can contain some adware which are not considered as malicious by many firms but not users.
ps. windows’ own dll and exe files are signed internally by microsoft so it can not be checked like i told by that simple method.