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#1
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Block cracking code from opening protected excel sheets
There is a code that has been found that opens our password protected files
even thought the sheet is protected is there a way to prevent this. AAAAABBAABBf typed in will unlock the sheet and now that the majority of people here know that I need to find a way to lock it up without having to use a password to open the file (people need to see the content). Does anyone know how to block this? |
#2
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Block cracking code from opening protected excel sheets
Hi,
You can't. No matter how complex an excel password is, Excel converts it into a 12 characters string. the first 11 characters are either A or B and the last is one of 95 characters in the ASCII range of 32 (space) to 126 (~Tilde) or 194,560 possible combinations so no matter what password you use one of those combinations will remove the password. There are several bits of code on the net that try each of those combinations in turn. In short Excel worksheet protection is to guard against inadvertant change and will not deter the malicious for more than a few moments. -- Mike When competing hypotheses are otherwise equal, adopt the hypothesis that introduces the fewest assumptions while still sufficiently answering the question. "Barbara" wrote: There is a code that has been found that opens our password protected files even thought the sheet is protected is there a way to prevent this. AAAAABBAABBf typed in will unlock the sheet and now that the majority of people here know that I need to find a way to lock it up without having to use a password to open the file (people need to see the content). Does anyone know how to block this? |
#3
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Block cracking code from opening protected excel sheets
It is pretty much as Mike H said - you cannot keep the determined out. Even
the term used "Protect" and "Unprotect" do not really imply "Security". For any given actual password, some combination that Mike described is going to come up with the same 'key' to unprotect the sheet. At this point all you could do would be to change the password ... and wait 5 minutes for someone to crack it again and pass the new alternative password around the office. "Barbara" wrote: There is a code that has been found that opens our password protected files even thought the sheet is protected is there a way to prevent this. AAAAABBAABBf typed in will unlock the sheet and now that the majority of people here know that I need to find a way to lock it up without having to use a password to open the file (people need to see the content). Does anyone know how to block this? |
#4
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Block cracking code from opening protected excel sheets
Don't confuse "protection" with "security". Sheet protection was never meant
to stop being from seeing data, it is only meant to preserve structure. As soon as you allow people to open the file containing the data, there is no way to stop them from accessing the data. (via macros, formula links, 3rd party software, etc). Depending on the nature of your data, you have several options, with varying degrees of security a) Have a 2nd workbook reference the original workbook via formulas. Displays data, but if someone changes the reference formula, they'll have access to your data. b) Require a password to open data workbook. Better, but there are still plenty of common 3rd party password cracker. c) Same as above, but encrypt with 128 bit or greater encryption. (Save as, tools, security options...) Better still, a few password crackers will be able to defeat this. d) Copy the pertinent info from data workbook to another workbook. Only share the 2nd workbook. Best "security" in that no one can access the info you don't want them to have, more tiresome to have to update, if necessary. -- Best Regards, Luke M "Barbara" wrote in message ... There is a code that has been found that opens our password protected files even thought the sheet is protected is there a way to prevent this. AAAAABBAABBf typed in will unlock the sheet and now that the majority of people here know that I need to find a way to lock it up without having to use a password to open the file (people need to see the content). Does anyone know how to block this? |
#5
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Block cracking code from opening protected excel sheets
as an additional comment, because 'someone' has come up with this string that
unlocks you worksheet it follows that have a copy of the code to produce it. An audit of PC's might discourage further attempts. You'r looking for a workbook called something like Password.xla -- Mike When competing hypotheses are otherwise equal, adopt the hypothesis that introduces the fewest assumptions while still sufficiently answering the question. "Mike H" wrote: Hi, You can't. No matter how complex an excel password is, Excel converts it into a 12 characters string. the first 11 characters are either A or B and the last is one of 95 characters in the ASCII range of 32 (space) to 126 (~Tilde) or 194,560 possible combinations so no matter what password you use one of those combinations will remove the password. There are several bits of code on the net that try each of those combinations in turn. In short Excel worksheet protection is to guard against inadvertant change and will not deter the malicious for more than a few moments. -- Mike When competing hypotheses are otherwise equal, adopt the hypothesis that introduces the fewest assumptions while still sufficiently answering the question. "Barbara" wrote: There is a code that has been found that opens our password protected files even thought the sheet is protected is there a way to prevent this. AAAAABBAABBf typed in will unlock the sheet and now that the majority of people here know that I need to find a way to lock it up without having to use a password to open the file (people need to see the content). Does anyone know how to block this? |
#6
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Block cracking code from opening protected excel sheets
Everyone has some good ideas for you, thought I'd offer just one more and it
kind of goes along with Mike H's second recommendation. Mine: put a 'rat' in the cell with the suspect and have them tell you who's unprotecting the sheet! Caveat: Since this relies on VBA/macro, if your workbook doesn't already have macros in it, then the presence of this set is going to raise some eyebrows and perhaps get people looking around. This is all Workbook event code, so it goes into the ThisWorkbook object's code module via VB. Just ask if you need to know how to get it to the proper place in the workbook. How it works: It checks when the workbook is opened to see if one specific sheet (one you specify in the code) is protected or not. It reports that condition, so now your report knows the state of that sheet's Protect setting. If it was already unprotected, we don't want to accuse an innocent of unprotecting it. If it was protected when opened, then as soon as someone unprotects it AND then selects a cell on that sheet, the fact that the sheet has become unprotected will be recorded along with the name of the individual logged into the system. Keep in mind that someone else just might have come along while the logged in user was away from the desk to do the dastardly deed. You need to: add a sheet to the workbook copy the code below into the ThisWorkbook object's code module and then set the Const NarcSheetName to the new sheet's name, and change the name of the Const WatchedSheetName to the name of the sheet that you want to keep an eye on. Close the VB Editor and save the workbook. One other thing you can try to do is to protect the VBProject with a password. This will help keep them out of your code and keep them from being able to unhide the reporting sheet. Be sure you write the VBProject's password down somewhere, it's harder to crack than workbook/worksheet passwords, but there are tools to get the job done. To protect the VB Project: while still in the VB Editor, choose Tools -- VBAProject Properties then on the [Protection] tab, check the box next to "Lock project for viewing" and enter and confirm the password for the project and hit the [OK] button. Actually, it's a good idea for you to keep a copy of the workbook without the password protection on the VBAProject, just in case you lose its password later. TO VIEW the report list, you have to open the workbook, go into the VB Editor (providing the password along the way), and then select the report worksheet and set its .Visible property to xlVisible (choice from dropdown list). Don't worry about hiding it again later, the Workbook_Open event will take care of that. At long last, here is the code: Private SecretReportMade As Boolean Private Const NarcSheetName = "Sheet3" Private Const WatchedSheetName = "Sheet1" Private Sub Workbook_Open() 'test to see if the sheet is unprotected when the 'workbook is opened, this will help prevent 'accusing the innocent of unprotecting it 'if it is unprotected, simply set the 'SecretReportFlag = True to prevent making 'any report later on ' 'make sure that the reporting sheet is invisible 'to anyone without going into the VB Editor ThisWorkbook.Worksheets(NarcSheetName).Visible = _ xlSheetVeryHidden SecretReportMade = _ Not ThisWorkbook.Worksheets(WatchedSheetName).ProtectC ontents CleanupTattleTaleList 'make row for new entry at top of the list ThisWorkbook.Worksheets(NarcSheetName).Rows("2:2") .Insert _ Shift:=xlShiftDown If SecretReportMade Then ThisWorkbook.Worksheets(NarcSheetName).Range("A2") = Now() ThisWorkbook.Worksheets(NarcSheetName).Range("B2") = _ WatchedSheetName & " Already Unprotected when opened by: " _ & Application.UserName Else ThisWorkbook.Worksheets(NarcSheetName).Range("A2") = Now() ThisWorkbook.Worksheets(NarcSheetName).Range("B2") = _ WatchedSheetName & " Was properly protected when opened by: " _ & Application.UserName End If End Sub Private Sub Workbook_SheetSelectionChange(ByVal Sh As Object, _ ByVal Target As Range) Dim WS As Worksheet If Sh.Name < WatchedSheetName Or _ SecretReportMade Then 'no work to do, quit Exit Sub End If If Not Sh.ProtectContents Then 'sheet is no longer protected, report who did it! ' Set WS = ThisWorkbook.Worksheets(NarcSheetName) 'make row for new entry at top of the list WS.Rows("2:2").Insert Shift:=xlShiftDown WS.Range("A2") = Now() ' record date/time of the entry WS.Range("B2") = _ Sh.Name & " Protection removed while in use by: " _ & Application.UserName SecretReportMade = True End If End Sub Private Sub CleanupTattleTaleList() 'this keeps the 'secret police' sheet from filling up 'and creating an error at some time in the future 'by removing to bottom 500 entries once it gets down 'beyond 2000 entries Dim lastRow As Long lastRow = ThisWorkbook.Worksheets(NarcSheetName).Range("A" & _ Rows.Count).End(xlUp).Offset(1, 0).Row If lastRow 2000 Then Application.DisplayAlerts = False ThisWorkbook.Worksheets(NarcSheetName).Rows("1500: " _ & lastRow).Delete Application.DisplayAlerts = True End If End Sub "Barbara" wrote: There is a code that has been found that opens our password protected files even thought the sheet is protected is there a way to prevent this. AAAAABBAABBf typed in will unlock the sheet and now that the majority of people here know that I need to find a way to lock it up without having to use a password to open the file (people need to see the content). Does anyone know how to block this? |
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