The United States has suffered another major classified data leak that allegedly contains spying activities on its key allies, including South Korea. Both countries are now scrambling to minimize the negative impact of the fiasco by claiming that most of the leaked documents were faked and reaffirming their bilateral alliance. But things are likely to become more embarrassing -- if not disturbing -- unless proper steps are taken.

It is not the first time that the US has failed to keep its secretive activities from being leaked online. In 2013, ex-CIA contractor Edward Snowden exposed the US’ extensive surveillance program. In 2015, WikiLeaks revealed that the US had wiretapped former German Chancellor Angela Merkel, as well as three French presidents.

But it is not easy to dismiss the latest leak involving Ukraine and US allies as a sorry incident that will be quickly forgotten. The cause for concern involves details and implications of what the leaked data disclosed.

According to the leaked documents reported by the New York Times over the weekend, South Korea had agreed to sell artillery shells to help the US replenish its stockpiles, but insisted that the US military should be the “end user,” reflecting concerns they may be relayed to forces in Ukraine. This would go against South Korea’s policy of not sending armaments into a war zone.

Shockingly, according to the secret Pentagon documents, top aides to President Yoon Suk Yeol expressed concerns that “the US would not be the end user if South Korea were to comply with a US request for ammunition.”

The revelation raises two serious questions. First, how did the US wiretap internal dialogue between Korea’s top officials on a sensitive issue involving Ukraine? Second, why did the US keep spying on its key allies?

As for the first question, the Ministry of National Defense on Monday denied allegations of security breaches at the ministry’s headquarters next to the presidential office. The ministry’s spokesperson said sufficient measures have been taken to prevent eavesdropping and wiretapping.

But the secret report was based on signal intelligence, which suggests the US had already penetrated into the Korean government’s networks and intercepted communications, possibly including phone and email.

As lawmakers from the main opposition Democratic Party of Korea have urged, the Yoon administration should demand accurate information on what happened from Washington regarding the wiretapping reports. Proper steps to remove wiretap devices, either by the US or Korea, should be done. If not, the US will likely continue to operate its spying activities on Korea, where stakes are high for geopolitical reasons such as the threats of North Korea and the growing belligerent influence of China.

Another question regards the essential function of spying. The latest leak shows that the US seems to be keen on collecting information on its allies’ internal decisions regarding Ukraine, despite its poor record on safeguarding classified data.

By securing the innermost discussions of its counterparts in secret, the US can be in a safe position to manipulate the behaviors of other governments -- including South Korea, one of its crucial allies -- to its own advantage.

If proven true that the US indeed kept collecting classified information through signal intelligence on Korea, it is clearly a shameless infringement on another country’s sovereignty. And it will lead to a crack in the “ironclad” alliance that South Korea and the US have jointly built up through mutual trust and cooperation.

Given the importance of the alliance, the Yoon administration has to work closely with the US to mend fences, especially ahead of the April 26 summit between Yoon and US President Joe Biden. It must also fix the presidential office’s security system, which is apparently vulnerable to eavesdropping. For its part, the US must stop its reprehensible surveillance practices that sow seeds of mistrust and doubt among allies.