An interlock is an alcohol interlock that controls vehicle starting based on factors such as the result of the driver's breath test, and it records what happens during tests and in the device's status. Fleet managers and installers may receive these records for periodic inspections, trip record reviews, and internal reports. If the supplier provides a comma-separated text file such as a CSV, you may want to open it in Excel to review it by time, vehicle, and event.
Even if the text is not garbled and appears as a table, that does not mean the file was read safely. Excel may interpret certain cells in a CSV as formulas instead of displaying them as text. The point of the check is to confirm that characters in the original did not act as calculations in the review view, without changing the meaning of the log's test values or events.
First establish what the log file is and what it is for
Not every interlock exports CSV files, and they do not all use the same column layout. If the data is designed to be read only in a dedicated program file or a supplier portal, do not open it by simply renaming its extension to CSV or an Excel file. Check the download path, file format, and recommended viewing program the supplier specifies first, to reduce the risk that the file structure changes or some fields go missing.
If the file really is a CSV, it is best to store the original separately and work on a copy made for viewing. The original is the record as the device or management system exported it at the time, while the copy is data imported or arranged to be easier for people to read. Keeping the two files apart prevents you from later mistaking results sorted and saved in a spreadsheet for the original record left by the device.
Formula interpretation is a different problem from character encoding
A CSV is a text file that does not fully store cell appearance or formatting on its own. When Excel opens a CSV, it may interpret each column based on its current default data format settings. So how date-like values are displayed, whether leading zeros in ID numbers are preserved, and how strings that look like formulas are handled are all separate from Korean character encoding.
In particular, if the first character of a cell is =, spreadsheet programs may interpret it as a formula. OWASP describes characters such as +, -, @, and tab and line break characters, which can also lead to the start of a formula, as things to examine. There is no need to assume that the interlock's test values and time values take this form, but if the actual file has columns entered by people, such as vehicle nicknames, driver identifiers, or management notes, there is reason to check those columns separately.
| What to examine | What to check | What to do after checking |
|---|---|---|
| File format | The export format and viewing method the supplier specifies | Open it with the specified program or import method |
| Columns entered by people | Fields such as nicknames and notes that actually exist in the file | Review whether they are read as text columns |
| Imported cells | The first character of the original text and how Excel interprets the cell | Confirm that it is text, not a formula |
| Processed copy | Added characters, conversions, whether it was saved | Record how it differs from the original and its intended use |
Confirm why you should import rather than open
If you open a CSV directly from the file explorer, Excel automatically interprets each column's content. Using Excel's text/CSV import feature instead lets you see the delimiter and column conversion results in a preview, and gives you room to decide whether to treat certain columns as text. Actual menu names and options may differ by Excel version, so if your organization has set an import procedure, it is best to follow it.
The purpose of setting columns to be read as text is to see certain strings exactly as recorded, without passing them to calculation. However, choosing a setting alone does not guarantee the same result in every spreadsheet program and in later use. It is safer to compare directly whether the cells you suspected remain as original text in the review copy, not as calculated results, and then make that method a repeatable procedure.
Take a hypothetical example. Suppose a vehicle's monthly CSV has a management note column alongside device events, and one row in it starts with =.... At the observation stage, compare that row in the original file with how the cell is displayed in Excel. At the interpretation stage, distinguish that this value is not an interlock test result but a string in the note column, which may be processed as a formula automatically. A possible action is to keep the original and open a copy using the import method, reading that column as text. The completion criterion is that the row appears in the copy as the original string, not as a calculated result, and the original file remains unmodified.
Do not mix display copies with data for re-entry
If you add a character in front or apply quoting to prevent formula interpretation, that character may remain as actual data. Even if a table shown to people looks fine, if that file is later uploaded again to another system, the vehicle identifiers or note content may be passed on as altered data. So if you make a processed copy for display, clearly label it as a copy for viewing, not a replacement for the original.
OWASP also explains that when a CSV is saved and reopened, quoting or escaping may change, and a formula that seemed blocked at first may become active again. That is why, rather than applying a single replacement rule found online to every log and calling it done, you need to check saving, reopening, and whether the file is passed on to the next system within the actual workflow. You must not deal with the risk by arbitrarily editing the test values, event times, or codes the device recorded.
When asking for help, show the problem row and how you opened it
If the export format or the meaning of a particular column is unclear, rather than sending only the file name to the supplier or the integration contact, it is better to explain which program you used, how you opened it, and what the problem column is for. For example, giving the file format, column name, viewing method, and program version separately, as in "when opening the CSV directly, one cell in the note column looks like a formula," helps narrow down what needs to be reproduced.
If test data is needed, do not share real driver information or entire trip records widely. Select only the range needed to reproduce the problem. What you ultimately need to keep is the original log, the purpose of the copy used for review, and which columns were read in which way. Keeping these apart prevents you from mistakenly transferring a calculated result on an Excel screen as a value recorded by the interlock device.
