President Barack Obama has ordered the shoring up of sanctions that the US could use against individuals and nations that attack the country with cyber tools and threats.
No new sanctions have been created, but Obama is keen to see existing measures applied with more force and frequency.
The US has used these tools before, and they were raised during discussions about the alleged North Korea attack on Sony Pictures.
The president presents his actions as a reaction to the real menace that is growing in scale and capability and continues to hurt US firms like Home Depot.
"I find that the increasing prevalence and severity of malicious cyber-enabled activities originating from, or directed by, persons located, in whole or in substantial part, outside the US constitute an unusual and extraordinary threat to the national security, foreign policy and economy of the US. I hereby declare a national emergency to deal with this threat," he said.
The response is a greater use of sanctions, and an increase in the powers available to the government, according to a White House blog post.
"We are at a transformational moment in how we approach cyber security. The actions we take today will help ensure that the internet remains an enabler of global commerce and innovation," said Lisa Monaco, US homeland security advisor to president Obama.
"We need to deter malicious cyber activity and to impose costs in response to the most significant cyber intrusions and attacks, especially when those responsible try to hide behind international boundaries.
"Effective incident response requires the ability to increase the costs and reduce the economic benefits from malicious cyber activity. We need a capability to deter and impose costs on those responsible for significant harmful cyber activity where it really hurts - at their bottom line."
Businesses such as the US Postal Service have been attacked with greater frequency over the past year and, while international entities are not always blamed, China is a regular suspect.
Sanctions can be imposed against a nation or an individual, and they are expected to be used only at times when US assets and infrastructure are under threat.
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