Congress relies on a variety of mechanisms, instruments, and procedures to protect classified national security and other sensitive information in its custody. Such information—most of which comes from the executive branch—can be hard to obtain. But accessibility to it is seen as necessary for the legislature to carry out its constitutional responsibilities, especially overseeing the executive and legislating public policy. The safeguards surrounding information deal with who is eligible for access, what information is made available and in what form, where and when it can be accessed, and how and in what circumstances or contexts it can be used afterwards. The relevant requirements and mechanisms include House and Senate security offices responsible for setting and implementing standards for safeguarding classified information; committee rules determining access to committee-held classified information, including what is made available and to whom, as well as how and under what conditions; committee and certain chamber rules governing how classified information can be used afterwards, in what contexts and forums, and under what conditions; establishment of special congressional groups to receive highly sensitive classified information; a secrecy oath required for all Members and employees of the House and several of its committees; security clearances and nondisclosure agreements for staff; and formal procedures for investigating suspected security violations. Public laws, House and Senate rules, and committee rules—as well as custom and practice, including informal agreements between legislators and executive officials—constitute the bases for these requirements and arrangements. Some of these have evolved over time, in response to changing conditions and needs of both the legislative and executive branches. The two chambers have approached their security program differently, although each now has an office of security and a set of requirements, instructions, and guidelines regarding the protection of classified and other controlled information. The Senate established an Office of Senate Security in 1987, the result of a bipartisan effort over two Congresses. It is charged with consolidating information and personnel security. Located in the Office of the Secretary of the Senate, the Security Office sets and implements uniform standards for handling and safeguarding classified and other sensitive information in the Senate's possession. The Security Office's standards, procedures, and requirements—detailed in its Senate Security Manual , first issued in 1988—"are binding upon all employees of the Senate." These cover committee and Member office staff and officers of the Senate as well as consultants and contract personnel—but not Members themselves. The regulations extend to a wide range of matters on safeguarding classified information: physical security requirements; procedures for storing materials; mechanisms for protecting communications equipment; security clearances and nondisclosure agreements for all Senate staff needing access; and follow-up investigations of suspected security violations by employees. In 2005, the House put its own security office in place—the Office of House Security (OHS)—under the jurisdiction of the House Sergeant at Arms, following approval of the chamber's Committee on House Administration. The office, similar to the Senate predecessor, is charged with developing an Operations Security Program for the House. Its responsibilities and jurisdiction encompass processing security clearances for staff, handling and storing classified information, managing a counterintelligence program for the House, and coordinating security breach investigations. Unlike its Senate counterpart, however, the House Office of Security has not issued an official security manual. Nonetheless, OHS provides relevant services, instructions, and forms for security clearances and other safeguards to protect classified information. Prior to the establishment of OHS, the chamber had relied on individual committee and Member offices to set requirements following chamber and committee rules, guidelines in internal office procedural manuals, and custom. Although there is no across-the-board, comprehensive requirement for all legislative branch staff, they are required to have security clearances and written nondisclosure agreements to gain access to classified information. These exist through various mechanisms, which apply to different employee categories: Each panel spells out its requirements in its rules to cover access. In addition, the Office of Senate Security and Office of House Security both require employees needing access to classified information to have security clearances and nondisclosure agreements in order to be eligible for access to classified national security information. A provision in the Senate Security Manual along these lines stipulates that "Senators and Committee Chairmen must determine which positions on their staffs require a security clearance. Clearances will only be granted to employees whose assignments require access to classified information." Individual Member offices may on their own require both clearances and nondisclosure agreements for staff to be eligible for access. Even so, requirements and limitations are directed by each chamber's office of security. A limit may also be imposed on the number of staff with clearances in any individual Member office. Along with this, congressional offices may on their own require a need-to-know for individual staffers seeking access to certain classified information. Security clearance requirements are included in the personnel manuals, job and position descriptions, or vacancy announcements of Congress's support agencies: Congressional Budget Office (CBO), Congressional Research Service (CRS) as well as the Library of Congress (LOC), and Government Accountability Office (GAO). The House and Senate differ with regard to secrecy oaths for Members and staff. Neither the full Senate nor any Senate panel apparently imposes a secrecy oath or affirmation on its Members or employees. The House, by comparison, has adopted such special procedures. Beginning with the 104 th Congress, the House has required a secrecy oath (taken once per Congress) for each Member, Delegate, Resident Commissioner, officer, and employee of the chamber. Before any such person may have access to classified information, he or she must solemnly swear (or affirm) that I will not disclose any classified information received in the course of my service with the House of Representatives, except as authorized by the House of Representatives or in accordance with its Rules. Previously, a similar oath was required only for Members and staff of the House Permanent Select Committee on Intelligence. This requirement had been added in the 102 nd Congress as part of the select committee's internal rules, following abortive attempts to establish it in public law. The oath is still in effect for the panel's Members and staff: I do solemnly swear (or affirm) that I will not disclose or cause to be disclosed any classified information received in the course of my service on the House Permanent Select Committee on Intelligence, except when authorized to do so by the Committee or the House of Representatives. At least one other panel has adopted a similar measure. The House Committee on Homeland Security requires an oath or affirmation from each committee Member or staff seeking access to classified information, modeled after the one adopted by the House Intelligence Committee. Procedures controlling access to classified information held by congressional offices exist throughout Congress. Although these differ, committee and chamber rules set conditions and requirements for sharing such information with other panels, Members, and staff. This includes determining: who may attend a panel's executive (or secret) session hearings; who is eligible for access to a committee's classified holdings; what information may be made available to all Members across-the-board; and if so, how, to what extent, and in what form; what specific committee-held information is to be made available to non-committee Members seeking access; a panel's requirements and conditions for access may depend on what the information covers (the specific subject matter and a need-to-know), to what extent it may be made available (all or only a part of it), in what form (e.g., the actual documents, a summary account, or a briefing from a committee Member or staff), under what restrictions (with or without staff in attendance or taking notes), or where (in the committee offices, most likely, or in a secure area elsewhere); and how and in what other forums (e.g., with another congressional panel or on the floor of the chamber) may the information be used and under what restrictions. The most exacting requirements along these lines have been developed by the House Permanent Select Committee on Intelligence; its rules are based on the committee's 1977 establishing authority and reinforced by intelligence oversight provisions in public law, such as the 1991 Intelligence Authorization Act. The panel's controls apply to select committee Members sharing classified information outside the committee itself as well as to non-committee Representatives seeking access to the panel's holdings. In the latter case, an individual requester must go through a multi-stage process to obtain access. Consequently, it is possible for a non-committee Member to be denied attendance at its executive sessions or access to its classified holdings; given only a briefing on it; granted partial access; or allowed full access. The select committee also sets rules on whether the Member may be accompanied by a cleared staffer or may take notes. When the House Select Committee on Intelligence releases classified information to another panel or non-member, moreover, the recipient must comply with the same rules and procedures that govern the intelligence committee's control and disclosure requirements. By comparison, rules of the House Armed Services Committee are to "ensure access to information [classified at Secret or higher] by any member of the Committee or any other Member, Delegate, or Resident Commissioner of the House of Representatives … who has requested the opportunity to review such material." Executive branch notification about intelligence activities, including presidential findings regarding covert operations, is usually provided directly to the House and Senate select committees on intelligence. These full panels, however, may be bypassed—based on the urgency of a situation, to meet extraordinary circumstances affecting the vital interests of the United States, or to protect the extremely sensitive nature of the information—in favor of notification to the so-called "Gang of Eight" or "Gang of Four." Notification about covert operations, in certain situations, is submitted to the statute-based "Gang of Eight," composed of the Speaker and minority leader of the House and chairman and ranking minority Member of its intelligence committee and the majority and minority leaders of the Senate and chairman and vice chairman of its intelligence committee.