A labor union representing 12,000 federal officers who issue immigration documents will join forces on Monday with the union representing deportation agents to publicly oppose a bill overhauling the immigration system that is making its way through the Senate, arguing that the legislation would weaken public safety.

The two unions represent a total of 20,000 employees in the Department of Homeland Security who would play a central role in carrying out the ambitious legislation, either by reviewing applications from millions of immigrants who could gain new legal status through the bill or by expelling illegal immigrants who did not qualify.

A letter to Congress that excoriates the Senate proposal, and that the immigration officers’ union signed for the first time, reveals simmering unrest among Homeland Security employees, who have been asked to carry out broad and fast-paced immigration policy shifts by the Obama administration. Deportation agents have been instructed to focus heavily on removing serious criminal offenders, while immigration officers have been urged to accelerate their decisions on granting legal papers and reprieves from deportation.

The criticism of the bill from inside the system gives new political fuel to its most staunch opponents — among them Senator Jeff Sessions, Republican of Alabama — when they had been battling on the defensive.

The labor alliance also raises the influence of the federal officer who leads the union that represents most deportation agents, the National Immigration and Customs Enforcement Council. The officer, Chris Crane, has emerged as a star witness for the opposition to the overhaul and a troublesome adversary for Obama administration officials working to promote it.

Mr. Crane first wrote to Congress on May 9, saying the Senate bill was tailored to meet the demands of “special interests,” and calling it “a dramatic step in the wrong direction” on public safety and interior enforcement. He said the proposal would give administration officials too much discretion in choosing which immigration laws to enforce. Mr. Sessions helped circulate Mr. Crane’s letter.

In a statement that the unions expected to release Monday — but that was given to some reporters on Sunday — Kenneth Palinkas, president of the National Citizenship and Immigration Services Council, said he had added his signature to Mr. Crane’s letter. Mr. Palinkas, whose union represents 12,000 employees of the agency that approves documents, said the officers had been “pressured to rubber stamp applications instead of conducting diligent case review and investigation.”

Support from another immigration union considerably strengthens Mr. Crane’s hand. Up to now, his law enforcement allies had been far outnumbered by groups that rallied behind the Senate bill and the White House. Also, Mr. Crane does not represent the more than 8,000 Immigration and Customs Enforcement agents who handle criminal investigations, hunting down human traffickers and drug smugglers. They have much smoother relations with the administration.

Mr. Crane has testified repeatedly this year in Capitol Hill hearings, mostly invited by conservative Republicans who reject any measure that would offer a path to citizenship to illegal immigrants. Although his delivery is measured and cool, Mr. Crane’s message is invariably scorching: he says the Obama administration has pandered to groups that advocate for those immigrants while hobbling the agents he represents, preventing them from doing their work.

Opponents of the bill, written by a bipartisan group of eight senators, are increasingly relying on Mr. Crane to bolster their case. Last week, another pillar of conservative resistance, the Heritage Foundation, was badly weakened when many Republicans dismissed a study it published on the bill’s costs. One author of the study, Jason Richwine, resigned under criticism of his past writings asserting that some immigrants had lower intelligence. Many conservative talk radio hosts are softening on the legislation.

But Mr. Crane is not holding any of his fire. At a hearing in February, he spoke shortly after his top boss, the secretary of homeland security, Janet Napolitano. He accused her point blank of running a department afflicted with “gross mismanagement and overall corruption.”

In April, Mr. Crane strode into the news conference where the eight senators who wrote the bill presented it to the public for the first time. He repeatedly raised his hand and asked the senators to “take a question from law enforcement.” Federal marshals finally stepped forward to march him out of the room.

With debate on the bill moving quickly in the Senate, Mr. Crane’s broadside attacks are a vexing irritant to administration officials, who argue that the time is right for Congress to offer a path to citizenship to millions of illegal immigrants because enforcement is stronger than ever. Claiming the authority of agents in the trenches, Mr. Crane depicts an almost opposite reality.

The sweeping Senate bill would offer legal status and eventually citizenship for an estimated 11 million illegal immigrants, tighten border security, and speed visa reviews for more than four million immigrants who have applied legally and are waiting in backlogs.

Homeland Security officials vehemently dispute Mr. Crane’s view of their enforcement record, saying he has used the guise of labor advocacy to pursue his own political agenda, aligning squarely with the most right-wing opponents of the overhaul. They point to official figures showing that the Obama administration has deported more than 1.4 million immigrants.

Last week, Latino and labor organizations called on President Obama to suspend most deportations, protesting that thousands of people from their communities are still being expelled each week.

In an interview in Salt Lake City, where he is based, Mr. Crane dismissed those groups as simply mistaken. “This department under this administration is doing anything and everything they can not to arrest any alien in the interior of the United States,” he contended.

Up to now, Mr. Crane had managed to speak loudly from a small platform. His national council represents about 7,700 of the 20,000 employees of Immigration and Customs Enforcement. Mr. Crane, who joined the agency 10 years ago after two tours of duty in the Marine Corps, was elected to a second term as union president in August.

State-sponsored hackers have renewed attacks on the US after a three-month hiatus, the New York Times reports.

In February, Unit 61398 of the Chinese army was named as the source of many cyber-attacks on American companies and federal agencies.

The publicity drew denials from the Chinese government, but also prompted the number of attacks launched from China to slow to a trickle.

Now, the newspaper reports, the unit has resumed attacks on US companies.

Cyber-defence company Mandiant told the New York Times the unit, which is believed to operate out of a heavily guarded building in the suburbs of Shanghai, had recently stepped up its activity. It declined to name which agencies and businesses had been attacked.

Earlier this year Mandiant published detailed evidence suggesting Unit 61398 was behind the vast majority of significant attacks on American federal agencies and industrial organisations.

Government documents, intellectual property, blueprints and many other confidential papers had been stolen during the attacks, said Mandiant.

According to Matasano, most cryptography is "pretty broken." Their evidence? 48 challenges.

Well, that's troubling. Ars does some honeypot investigating to show that Microsoft can and does intercept and read some Skype traffic.

Greg puts up a textbook answer.