It claims that Microsoft offers better indemnification than any Linux vendor and has highlighted specific problems with the indemnification policy of each vendor, although it has not yet divulged the specific details of its own policy.
"Microsoft is doing more to stand behind its products with meaningful indemnification than the leading distributors of the Linux operating system, namely Novell, Red Hat or HP," a Microsoft spokeswoman told ZDNet UK on Thursday. "IBM has never indicated it offers IP indemnification for Linux."
This follows Microsoft's initial criticism of IP indemnification in an executive email written by its CEO Steve Ballmer.
Microsoft focused its criticism on Red Hat, saying that the Linux distributor does not assist customers with legal expenses.
"Red Hat doesn't offer indemnification; instead, they offer a limited warranty," said the spokeswoman. "The warranty does not offer any compensation for legal fees if a customer is caught in the middle of an IP dispute."
Bryan Sims, the vice-president of business development at Red Hat, told ZDNet UK that it does not offer legal expenses to customers, but claimed the threat of legal action was not the main concern of its customers.
"The warranty programme was set up so customers would have uninterrupted use of software -- customers were not as interested in protection against lawsuits," said Sims. "The main risk for the end user is that they have deployed something and won't be able to use it for a mission-critical function."
Sims claimed that it was more likely for the software company responsible for the product to be sued, rather than the end user of a product. "It is very rare that an end user is sued by another software company," said Sims.
Struan Robertson, a lawyer with law firm Masons, agreed it is unlikely for the end user to be sued, but is possible -- as was seen when SCO Group attempted to sue DaimlerChrysler and AutoZone for using Linux.
Red Hat does provide legal protection to those who develop applications for the Linux platform.
Microsoft criticised HP for only providing protection against a SCO lawsuit and claimed that HP used its indemnification to force customers to continue using its hardware.
"HP's indemnification covers only claims brought by SCO. HP uses its indemnification provision to lock customers into buying both HP hardware and HP support agreements. Plus, if you modify one line of your Linux code, you waive your entire coverage."
HP was unable to comment in time for this article. Lock-in is an issue which Microsoft has been criticised for numerous times in the past, including this week when it was announced a nine-year contract with the NHS.
Microsoft also pointed the finger at Novell for only offering protection against copyright-related claims.
"Novell's public statements indicate the indemnification only covers copyright-related claims -- it does not provide any coverage for patent-, trade secret- and trade mark-related claims," said the spokeswoman, "In contrast, Microsoft's indemnification covers all four of these claim types"
Novell was unable to comment in time for this article. Richard Penfold, a partner in the IP practice of law firm DLA, told ZDNet UK that copyright is the most common IP claim against software, due to the nature of software. He said that although software is patentable, infringement claims can be difficult to prove.
Penfold said that Novell offers up to $1.5m in damages, while Microsoft has not yet revealed at what level it caps damages.