Purpose

In order to make certain issues be viewed only to a certain group/roles and they shouldn't be able to edit that Issue.

Solution

1. Create a Project Role Eg: "Silent Viewers" - https://confluence.atlassian.com/display/JIRA/Managing+Project+Roles#ManagingProjectRoles-Addingaprojectrole. If each project in your JIRA instance should have different users attached to this Role then you could add them from - https://confluence.atlassian.com/display/JIRA/Managing+Project+Role+Membership#ManagingProjectRoleMembership-Assigningausertoaprojectrole. This is because Roles can have users that are globally available in all projects and could also have certain users available for certain projects
2. Create an Issue Security Scheme for this - https://confluence.atlassian.com/display/JIRA/Configuring+Issue-level+Security#ConfiguringIssue-levelSecurity-Creatinganissuesecurityscheme
3. Create a Security Level for the Issue Security Scheme (Eg: Only Silent Viewers) - https://confluence.atlassian.com/display/JIRA/Configuring+Issue-level+Security#ConfiguringIssue-levelSecurity-Addingasecurityleveltoanissuesecurityscheme
4. Setting the Default Security Level for an issue security scheme - https://confluence.atlassian.com/display/JIRA/Configuring+Issue-level+Security#ConfiguringIssue-levelSecurity-SettingtheDefaultSecurityLevelforanissuesecurityscheme
5. Assign the Role to the Security Level - https://confluence.atlassian.com/display/JIRA/Configuring+Issue-level+Security#ConfiguringIssue-levelSecurity-AddingUsers/Groups/ProjectRolestoaSecurityLevel
6. Assign Issue Security Scheme to the relevant project - https://confluence.atlassian.com/display/JIRA/Configuring+Issue-level+Security#ConfiguringIssue-levelSecurity-assign_issuesecurityschemeAssigninganissuesecurityschemetoaproject
7. Make sure that users from the Project Role created previously don't have Edit Issues project permission in the project permission scheme (This is because the users in the role created might also be in other groups/roles which have Edit Issues project permission in the project permission scheme) - https://confluence.atlassian.com/display/JIRA/Managing+Project+Permissions
8. Then set Security on the issue you want the above required behavior - https://confluence.atlassian.com/display/JIRA/Setting+Security+on+an+Issue