The cyber-attack, originally reported by Hotline's Erin McPike, left the following message on the site of Republicans on the House Oversight committee:
"F—- OBAMA!! Red Eye CREW !!!!! O RESTO E HACKER !!! by HADES; m4V3RiCk; T4ph0d4 — FROM BRASIL."
According to McPike, the Red Eye Crew has claimed responsibility for previous web infiltrations, including the sites for Old Dominion University in 2008 and advertising agency Wieden and Kennedy.
Politico reports similar messages were found on the Web sites of Reps. Joe Wilson (R-S.C.), Peter Welch (D-Vt.), Duncan Hunter (R-Calif.), Phil Roe (R-Tenn.), Charlie Wilson (D-Ohio), John Tierney (D-Mass.), Charles Gonzales (D-Texas), Brian Baird (D-Wash.), John Barrow (D-Ga.), Mark Kirk (R-Ill.), John Boccieri (D-Ohio), John Olver (D-Mass.), Bobby Bright (D-Ohio), Mike Coffman (R-Colo.), Travis Childers (D-Miss.), Andre Carson (D-Ind.), John Campbell (R-Calif.), Suzanne Kosmas (R-Fla.), Zoe Lofgren (D-Calif.) and other members.
A security review is expected to be ordered by House Speaker Nancy Pelosi, a Democratic leadership aide told Politico.
The attack comes after four men were arrested earlier this week for allegedly tampering with the phones in Democratic Sen. Mary Landrieu's office.
Update, 3:00 p.m. EST
The alleged hacker attack affected 49 House computer systems, reports CBS News' Jill Jackson.
All of the sites are maintained by GovTrend, an Arlington, Va.-based Web company. A similar attack took place in August, at which time GovTrend was reminded to keep up necessary security measures.
The company is currently working to restore the sites. But if they can't get the sites running in a reasonable amount of time, the Chief Administrative Officer of the House will step in and redirect users to a temporary shell page with basic contact information and an explanation of what happened, CAO spokesman Jeff Ventura told CBS News.
The CAO is investigating the matter and officials are discussing how to deal with GovTrend in the wake of the incident.
The following is a list of the offices and committees affected: