What is a .CUID2 file?
A .CUID2 file is a type of hidden file that is created by certain mobile applications which incorporate the Baidu software development kit (SDK). Popular apps like ES File Explorer and WeChat are examples of apps that might generate these files. The .CUID2 file stores sensitive information such as your mobile device's unique identifier (ID) and your International Mobile Equipment Identity (IMEI). This data is encrypted with a strong 128-bit AES encryption method to protect it.
However, despite the encryption, the purpose of .CUID2 files can be concerning. They are specifically used to share your device's ID and IMEI with third-party entities without your explicit consent. This happens because apps using the Baidu SDK may transfer these .CUID2 files to locations on your device that are accessible to other apps. For instance, these files might be placed in a directory like SD card's backups/.SystemConfig, which is not strictly protected. As a result, other apps can access these files and, by extension, the sensitive information they contain, without needing to ask for your permission.
Currently, there are no mainstream programs specifically designed to open .CUID2 files, primarily because these files are not meant to be accessed by users but are used internally by other applications.
More broadly, Baidu, the Chinese technology company behind the SDK, is known for its internet-related services and products. The creation of .CUID and .CUID2 files on user devices is an example of how apps developed with Baidu's technology might handle user data, often sharing it without user consent. This practice raises concerns about privacy and the security of personal information.
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