Here is my suggestion:
1. Whilst displaying the Incident List, click on Show Filter.
2. In the filter, type in the area in Incident Area (e.g. "Email") and click Search.
3. Scroll to the bottom of the page. At the lower right of the list, note the total number of records (e.g. 1-25 of 500); on the bottom of the list at the lower left, notice that there is a "View All ($)" function. Click on "View All".
Here is a screenshot from my system (I happen to have 28 records in total, not 500)
4. Scroll to the top of the page. On the upper right, click on the "Edit in List" button. The first entry in the list is automatically highlighted.
5. Type in the value of the status that you require (e.g. "Closed"). The Status field of the first entry in the list is automatically changed (but not saved). The status value for the entry is highlighted.
6. Click on "Change All" button which is above the fields displayed when you clicked "Edit in List".
The Status field of all entries in the list is changed to Closed. The status values are highlighted.
7. Click the "Save" button.
Notes:
1. As mentioned in other updates, change via backend is not recommended (nor officially supported).
2. Keep in mind that the update may take some time to complete successfully.
3. If you want to do the above page by page with list larger than 25 per page, you could configure the maximum for the lists but this would affect all lists displayed in the system, not just the edit-in-list for the Incident List. And so, you could instead use the filter to further restrict the number of entries returned; that is, for example, restrict by Area and by Earliest Open Date, increasing Open Date for subsequent filters.
4: Be sure that the status transitions for incidents are configured such that the change of the original Status to the desired Status (of Closed, in this case) succeeds, or follow the transitions according to the valid status transitions configured in your system. (e.g. change Open to In Progress, followed by changing In Progress to Closed).