LM-X can perform a clock check on the client side when calling LMX_Checkout() to ensure users have not backdated or tampered with their system clock. If tampering is detected, the user will be unable to check out the license and will be given an error regarding the invalid system clock time. The license server does a background check every 10 minutes, and if the clock has been tampered with, the license server shuts down.
This helps prevent unauthorized use of the software; for example, a user attempting to extend the end date of a trial license. Note that any clock discrepancy of less than 24 hours will not be detected as tampering. For example, a user can change the clock to reflect a different time zone without causing an error.
Whether a system clock check is done by default depends on the type of license, as follows:
| License Type | Default System Clock Check Behavior |
|---|---|
| Local | Check system clock only when end date is set. Otherwise, do not check system clock. |
| Network | Do not check system clock. |
| Trial | Check system clock. |
| Grace | Do not check system clock. |
| Borrow | Do not check system clock. |
The system clock check evaluates several criteria to determine whether the system time has been tampered with. Under some circumstances, the check can return a false positive. For example, a user might accidentally change the clock to a future time. Normally, the user can reset the system clock to the correct time to resolve the issue; however, in some cases this may not work.
To resolve such individual cases, you can send the user the LmxResetSystemClock tool (included in the LM-X distribution). The user can run this tool to fix the problem in most cases. The following shows an example of running the LmxResetSystemClock tool:
C:\lm-x>lmxresetsystemclock.exe
LM-X Reset System Clock Utility v3.5
Copyright (C) 2002-2010 X-Formation. All rights reserved.
Number of fixes: 2
To help prevent intentional misuse of the tool, you should limit its distribution to users you determine have a legitimate need. The tool runs only three times on a given machine, which provides an additional safeguard against users who may be attempting to gain unauthorized use of your software by tampering with the system clock.
To avoid such issues altogether, you can disable the clock check in the supplied license file. However, this is not recommended if you are concerned about unauthorized use of your software. See the SETSYSTEMCLOCK description in FEATURE settings for details about disabling the system clock check.