Dropbox is on the defensive after revealing its file-sharing service will in future tap into the very heart of your computer’s operating system.

Project Infinite, unveiled in April, will take Dropbox out of the browser on the PC or Macs and integrate it directly with your machine’s local file storage.

Items stored in your Dropbox account will show up in your machine’s local menus.

According to Dropbox, the browser is “a clunky user experience at best” but it means you will be able to shovel files into the Dropbox cloud more seamlessly.

The feature received the standard round of criticism-free approval and coverage from the luvvies of the start-up and consumer press. But this week Dropbox revealed how Project Infinite works – and it’s not been received at all well.

Project Infinite employs kernel extensions that’ll move from it from accessing your system’s user space and into the kernel space. Tapping the kernel isn’t a new or unique idea but it is generally reserved for more mission-critical applications, such as security or antivirus.

Giving any piece of software access to the kernel is a huge step, as it gives a potential hacker unfettered access to your system’s memory and processes. Also, you’re potentially leaving yourself wide open to faults and failing in the software author’s code, as some users of certain antivirus software brands can attest to.

In Windows, Dropbox will implement Microsoft’s Copy Hook Handlers, COM objects implemented as DLLs and called by the operating system shell. To penetrate OS X’s BSD kernel, Dropbox will employ Kernel Authorisation to manage the file authorisations.

If Dropbox had expected a smooth ride, hushed awe and general reverence to flow from its sharing the details of Project Infinite’s guts it received a rude surprise.

A commenter responding on the Dropbox blog named Jonathan gave them both barrels:

Antivirus has a terrible track record of slowing down computers and instability and generally being an ineffective nuisance. Device drivers also (especially graphics card drivers) are a common cause of instability. But yes, please come on in and fuck up my kernel. You obviously can't be trusted if you seriously think this is a good idea, and I'll be removing your software from every device I use. Process isolation is meant to protect users from bad software developers like you guys apparently are.

Among those asking if they could opt out of kernel access on the Dropbox blog was one Craig Burke. “I don't personally need to guard against the 'untrained intern problem' and I'm very uncomfortable with needing to load a kernel extension,” he wrote.

CVertex wrote: “Very exciting! Like many people, I'm cautious due to possible security compromises opened through kernel drivers.”

Dropbox was left flubbering for a response on Wednesday.

“We’ve been running this kernel extension internally at Dropbox for almost a year and have battle-tested its stability and integrity,” Dropbox wrote, adding: “After careful design and consideration, we concluded that this kernel extension is the smallest and therefore most secure surface through which we can deliver Project Infinite.”

The statement continued: “We understand the concerns around this type of implementation, and our solution takes into consideration the security and stability of our users’ experience, while providing what we believe will be a really useful feature.” ®