BENGALURU: US law firms have begun circling Infosys to investigate whether they have grounds to file a class-action lawsuit against the company, after a whistleblower alleged the company was using aggressive accounting tactics to boost revenue and margin.Rosen Law Firm, which specialises in securities class actions, put out an Infosys Loss Notice stating it ‘continues to investigate potential securities claims on behalf of shareholders.“Rosen Law Firm is preparing a class action lawsuit to recover losses suffered by Infosys investors,” the law firm said in a statement.Such notices are common in the case of US-listed stocks when there is material negative news that leads to a drop in the stock price.ET had reported on Monday that a group calling itself “ethical employees” had filed a whistleblower statement with the Infosys board and the US Securities & Exchange Commission, alleging that the company’s top managers were bending rules with regard to accounting of revenue from large deals and the profit margins.