Officials said the website was hacked early Saturday and it has been rendered inaccessible since then.
They said messages were posted on the link like "Pakistan Zindabad" and "we are team Pak cyber attacker".
The website, which acts as an official communicator for official work between the Central Board of Direct Taxes and the IT department field offices in the country, has put up a message saying, "We'll be back soon! Sorry for the inconvenience but we're performing some maintenance at the moment."
The technical team handling the website has sent a report in this regard to the Computer Emergency Response Team of India (CERT-In), which is the nodal agency to combat hacking, phishing and to fortify security-related defences of the Indian Internet domain.
They said a security audit is being undertaken of the online portal and added that no sensitive or secret information was uploaded on the said Universal Resource Locator (URL) of the IRS community working in the IT department.
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