The partial U.S. government shutdown is now into its fourth week, making it the longest-ever political standoff of its kind.

While critical functions such as defense and mail delivery still are operating, other less-vital units have been mothballed, including several national parks and many Washington, D.C., monuments. A handful of agencies are somewhere in between, furloughing some nonessential workers while keeping essential ones at work to maintain the absolutely necessary aspects of their service.

The ripple effect of the shutdown, however, has extended well beyond the circle of government employees and agencies. While government shutdowns typically don't hamper the stock market, a few publicly traded stocks and privately owned companies are starting to feel the pinch. These firms either provide contracted services and goods for the government, or cater to government employees who (for now) aren't receiving a paycheck.

Here are seven companies that have been (or that analysts think could be) adversely impacted by the shutdown.

Oracle

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Most arms) Office 365 for US Government. The CIA has tapped Amazon.com's () Amazon Web Services unit to build a private cloud. International Business Machines () soon-to-be-subsidiary Red Hat () has been one of the few outfits to divulge how much of its revenue comes from government customers (10% for the past three years).