A system comprising: a redundant control system comprising a plurality of controllers configured to control an industrial process, wherein each controller of the plurality of controllers comprises a secure repository, and wherein the control system is configured to: receive a login credential at each controller, wherein the login credential is a synchronised login credential so that each controller includes a similar copy of the login credential; encrypt and store the login credential in the secured repository of each controller in the redundant control system; and perform a security check of the redundant control system by using the login credential, comprising, at one of the controllers: accessing the stored login credential of the controller; decrypting the accessed login credential; authenticating the decrypted login credential by matching the decrypted login credential against a read login credential, wherein the read login credential is a user input login credential; successfully authenticating the decrypted login credential upon successful matching; and when the decrypted login credential is successfully authenticated, comparing it to a login credential of each of the other controllers to confirm that the login credentials are still synchronised and valid; wherein when, upon the comparing, the security check indicates that there is a login credential inconsistency between the plurality of controllers: providing an indication of a possible controller system tampering; arranging for the controls to vote to determine a next action to take based on the state of each controller. a redundant control system comprising a plurality of controllers configured to control an industrial process, wherein each controller of the plurality of controllers comprises a secure repository, and wherein the control system is configured to: receive a login credential at each controller, wherein the login credential is a synchronised login credential so that each controller includes a similar copy of the login credential; encrypt and store the login credential in the secured repository of each controller in the redundant control system; and perform a security check of the redundant control system by using the login credential, comprising, at one of the controllers: accessing the stored login credential of the controller; decrypting the accessed login credential; authenticating the decrypted login credential by matching the decrypted login credential against a read login credential, wherein the read login credential is a user input login credential; successfully authenticating the decrypted login credential upon successful matching; and when the decrypted login credential is successfully authenticated, comparing it to a login credential of each of the other controllers to confirm that the login credentials are still synchronised and valid; wherein when, upon the comparing, the security check indicates that there is a login credential inconsistency between the plurality of controllers: providing an indication of a possible controller system tampering; arranging for the controls to vote to determine a next action to take based on the state of each controller. receive a login credential at each controller, wherein the login credential is a synchronised login credential so that each controller includes a similar copy of the login credential; encrypt and store the login credential in the secured repository of each controller in the redundant control system; and perform a security check of the redundant control system by using the login credential, comprising, at one of the controllers: accessing the stored login credential of the controller; decrypting the accessed login credential; authenticating the decrypted login credential by matching the decrypted login credential against a read login credential, wherein the read login credential is a user input login credential; successfully authenticating the decrypted login credential upon successful matching; and when the decrypted login credential is successfully authenticated, comparing it to a login credential of each of the other controllers to confirm that the login credentials are still synchronised and valid; accessing the stored login credential of the controller; decrypting the accessed login credential; authenticating the decrypted login credential by matching the decrypted login credential against a read login credential, wherein the read login credential is a user input login credential; successfully authenticating the decrypted login credential upon successful matching; and when the decrypted login credential is successfully authenticated, comparing it to a login credential of each of the other controllers to confirm that the login credentials are still synchronised and valid; wherein when, upon the comparing, the security check indicates that there is a login credential inconsistency between the plurality of controllers: providing an indication of a possible controller system tampering; arranging for the controls to vote to determine a next action to take based on the state of each controller. providing an indication of a possible controller system tampering; arranging for the controls to vote to determine a next action to take based on the state of each controller.