The current US government closure is leaving dozens of insecure or inaccessible official websites.
Affected websites include the US Department of Justice, the Court of Appeals and NASA.
The closure, for a funding dispute for President Trump Mexican Wall, means that 400,000 federal employees are not currently paid.
One of the side effects of this is that security certificates for websites are not renewed.
Digital certificates ensure that communications between devices and websites are sent in an encrypted, secure way and are an essential part of keeping the IT infrastructure up and running. But, once issued, an expiration date of anything between a few months and several years is given.
- So, why did the US government shut down?
- When the obsolete code causes chaos
The losing ground
According to the Netcraft Internet Services website, more than 80 security certificates used by the .gov sites have expired.
This includes the United States Department of Justice, which is using a certificate expired in the week before the closure and has not been renewed since.
The newly created cybersecurity security of the Department of Homeland Security The Infrastructure Security Agency, is currently operating with less than half the staff, according to Suzanne Spaulding, a former agency official.
He said: "Every day that passes, the impact of the closure of the government on the security of our nation increases.In the meantime, our opponents do not miss a moment and continue the daily attacks on our systems.
"Computer security is quite difficult with a complete team. Operating with less than half of the forces means we are losing ground against our opponents. "
Security consultant Paul Mutton, writing in a blog for Netcraft, added:" With Donald Trump, he is apparently not willing to compromise his demands for a wall along the Mexican border and with the Democrats. who refuse to approve a budget containing $ 5.7 billion (£ 4.46 billion) for the wall, the hundreds of thousands of unpaid federal employees may not be the only ones to suffer.
"As more and more certificates used by government websites inevitably expire in the days that follow, weeks ̵