All EXE/DLL files in sysinternals tools are now signed with signature from Microsoft. You can:
1) Right click and select Properties, then change to Digital Signatures tab and open the cert that used to sign it and see if it's valid.
2) If you have the Visual Studio installed, you can open the "development command prompt for VS20XX", and use "signtool verify /all /pa <your exe/dll filename>" to verifiy them.
3) If you have older version of Sysinternal Tools Suite, you may also consider verify with SigCheck.